Wasps, Social and Solitary
by George W. Peckham · English · Gutenberg #47508 · 385,386 chars · public domain (US)
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Title: Wasps, Social and Solitary
Author: George W. Peckham
E. G. Peckham
Illustrator: J. H. Emerton
Release date: December 1, 2014 [eBook #47508]
Most recently updated: October 24, 2024
Language: English
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WASPS
SOCIAL AND SOLITARY
[Illustration:
Page 266
PELOPÆUS ON NEST, GROUP OF FINISHED CELLS, AND TUBE OPENED TO SHOW
SPIDERS]
WASPS
SOCIAL AND SOLITARY
BY
GEORGE W. PECKHAM
AND
ELIZABETH G. PECKHAM
WITH AN INTRODUCTION BY
JOHN BURROUGHS
_ILLUSTRATIONS BY JAMES H. EMERTON_
“Bold sons of air and heat, untamed, untired.”—ILIAD, Book XVII
[Illustration: LOGO]
BOSTON AND NEW YORK
HOUGHTON, MIFFLIN AND COMPANY
The Riverside Press, Cambridge
1905
COPYRIGHT 1905 BY GEORGE W. PECKHAM AND ELIZABETH G. PECKHAM
ALL RIGHTS RESERVED
_Published April, 1905_
NOTE
A PART of the matter presented in this volume was published several
years ago by the Wisconsin Biological Survey, under the title
“Instincts and Habits of the Solitary Wasps.” These chapters have
been revised and modified, and new matter based upon later work has
been added, in the hope that in their present less technical form the
observations recorded will be of interest to the general reader.
For a number of the text cuts used in this volume we are indebted to
the courtesy of Dr. E. A. Birge, Director of the Wisconsin Geological
and Natural History Survey.
CONTENTS
CHAPTER PAGE
I. COMMUNAL LIFE 1
II. AMMOPHILA AND HER CATERPILLARS 15
III. THE GREAT GOLDEN DIGGER 56
IV. SEVERAL LITTLE WASPS 72
V. CRABRO 97
VI. AN ISLAND SETTLEMENT 119
VII. THE BURROWERS 141
VIII. THE WOOD–BORERS 178
IX. THE SPIDER–HUNTERS 196
X. THE ENEMIES OF THE GRASSHOPPER 248
XI. WORKERS IN CLAY 265
XII. SENSE OF DIRECTION 275
XIII. INSTINCT AND INTELLIGENCE 292
LIST OF ILLUSTRATIONS
PAGE
PELOPÆUS ON NEST, GROUP OF FINISHED CELLS, AND
TUBE OPENED TO SHOW SPIDERS (page 266) _Frontispiece_
WASP EATING 3
PAPER NEST WITH SIDE REMOVED TO SHOW CONSTRUCTION
OF COMBS 11
AMMOPHILA URNARIA CARRYING CATERPILLAR TO
NEST 19
AMMOPHILA URNARIA STINGING CATERPILLAR 27
CATERPILLAR WITH EGG OF AMMOPHILA URNARIA 29
NEST OF AMMOPHILA 31
AMMOPHILA URNARIA USING STONE TO POUND DOWN
EARTH OVER NEST 39
THOROUGH LOCALITY STUDY BY SPHEX 59
HASTY LOCALITY STUDY BY SPHEX 61
SPHEX DRAGGING GRASSHOPPER TO HER NEST 63
NEST OF SPHEX 69
OXYBELUS QUADRINOTATUS 75
NEST OF OXYBELUS 79
APORUS FASCIATUS 81
WASP HOMES IN THE LOG CABIN 85
NEST OF PERENNIS 89
NEST OF ANORMIS 91
SEXMACULATUS IN THE LINDEN ROOTS 99
CRABRO AND HER WHITE MOTHS 103
CRABRO STIRPICOLA 106
BOTTLE ON STEM TO MEASURE WORK OF CRABRO 107
NEST OF C. STIRPICOLA 113
AMMOPHILA SLEEPING IN THE GRASS (AFTER
BANKS) 115
NEST OF BEMBEX 125
BEMBEX SPINOLÆ LOOKING OUT OF NEST 131
BEMBEX 136
A CORNER OF THE BEMBEX COLONY 137
NEST OF CERCERIS NIGRESCENS 142
CERCERIS CLYPEATA 143
CERCERIS DESERTA: LOCALITY STUDY BEFORE LEAVING
NEST 153
PHILANTHUS PUNCTATUS 157
NEST OF PHILANTHUS PUNCTATUS 163
APHILANTHOPS GATHERING ANTS 169
TRYPOXYLON RUBROCINCTUM 185
MALE TRYPOXYLON AWAITING THE FEMALE 191
TORNADO WASP (POMPILUS QUINQUENOTATUS) DIGGING
NEST 197
POMPILUS QUINQUENOTATUS 199
EPEIRA STRIX PARALYZED AND HUNG UP ON BEAN
PLANT BY POMPILUS QUINQUENOTATUS, OUT OF
THE WAY OF ANTS 203
NEST OF P. QUINQUENOTATUS 213
POMPILUS MARGINATUS 223
THE HOME–COMING OF SCELESTUS 241
NEST OF AGENIA BOMBYCINA 244
LYCOSA KOCHII, FOUND IN NEST OF AGENIA BOMBYCINA
245
TACHYTES 249
NEST OF TACHYTES 251
CHLORION AND THE INDISCREET CRICKET 257
HORIZONTAL CELLS OF THE MUD–DAUBER 271
COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN
FINDING HER SPIDER, AND IN RETRACING HER
STEPS TO THE NEST 283
LOCALITY STUDY OF ASTATA BICOLOR 288
LOCALITY STUDY OF ASTATA UNICOLOR 289
SECOND LOCALITY STUDY OF ASTATA UNICOLOR 290
PARALYZED SPIDER HUNG UP ON SORREL BY QUINQUENOTATUS
WHILE SHE DIGS HER NEST 295
Introduction
NOT long since I wrote to a friend, a nature lover, as follows: “The
most charming monograph in any department of our natural history that I
have read in many a year is on our solitary wasps, by George W. Peckham
and his wife, of Wisconsin,—a work so delightful and instructive that
it is a great pity it is not published in some popular series of
nature books, where it could reach its fit audience, instead of being
handicapped as a State publication.” This end has now been brought
about, and the book—revised and enlarged with much new material and
many new illustrations—placed within easy reach of all nature lovers,
to whom it gives me pleasure to commend it. It is a wonderful record
of patient, exact, and loving observation, which has all the interest
of a romance. It opens up a world of Lilliput right at our feet,
wherein the little people amuse and delight us with their curious human
foibles and whimsicalities, and surprise us with their intelligence
and individuality. Here I had been saying in print that I looked upon
insects as perfect automata, and all of the same class as nearly alike
as the leaves of the trees or the sands upon the beach. I had not
reckoned with the Peckhams and their solitary wasps. The solitary ways
of these insects seem to bring out their individual traits, and they
differ one from another, more than any other wild creatures known
to me. It has been thought that man is the only tool–using animal,
yet here is one of these wasps, Ammophila, that uses a little pebble
to pound down the earth over her nest. She takes the pebble in her
mandibles, as you or I would take a stone in our hand, and uses it as
a hammer to pound down the soil above the cavity that holds her egg.
This is a remarkable fact; so far as I know there is no other animal on
this continent that makes any mechanical use of an object or substance
foreign to its own body in this way. The act stamps Ammophila as a
tool–using animal.
I am free to confess that I have had more delight in reading this book
than in reading any other nature book in a long time. Such a queer
little people as it reveals to us, so whimsical, so fickle, so fussy,
so forgetful, so wise and yet so foolish, such victims of routine
and yet so individual, with such apparent foresight and yet such
thoughtlessness, finding their way back to the same square inch of
earth in the monotonous expanse of a wide plowed field with unfailing
accuracy, and then at times finishing their cell and sealing it up
without the spider and the egg; hardly any two alike; one nervous
and excitable, another calm and unhurried; one careless in her work,
another neat and thorough; this one suspicious, that one confiding;
one species digging its burrow before it captures its game, others
capturing the game and then digging the hole; one wasp hanging its
spider up in the fork of a weed to keep it away from the ants while
it works at its nest, and then running to it every moment or two to
see that it is safe; another laying the insect on the ground while it
digs,—verily a queer little people, with a lot of wild nature about
them, and of human nature, too.
JOHN BURROUGHS.
WASPS
Social and Solitary
Chapter I
COMMUNAL LIFE
“For where’s the state beneath the firmament
That doth excel the wasps’ for government.”
“What is not good for the swarm is not good for the wasp.”
AS the tendency of mankind to crowd into towns grows stronger the joys
of country life and the workings of Nature are more and more excluded
from the daily experience of humanity. In a few the primal love of
the wild is too strong for suppression, and turning from the hot and
noisy streets they find it a refreshment of spirit to meet our little
brothers of earth and air in the wider spaces of their own territory.
We were walking through the woods one hot day in the middle of August
when our attention was attracted by a stream of yellow–jackets
issuing from the ground. They came in such surprising numbers and
looked so full of energy that we stopped to watch them, and this was
our introduction to the study of these “bold sons of air and heat,”
although a perusal of Fabre’s fascinating “Souvenirs Entomologiques”
had prepared us to feel a lively interest in them. We were at our
summer home near Milwaukee, where meadow and garden, with the wooded
island in the lake close by, offered themselves as hunting grounds,
while wasps of every kind, the socialistic tribes as well as the
extreme individualists of the solitary species, were waiting to be
studied.
The Vespas that had aroused our interest received our first attention,
and a nest in the ground proved to be a most convenient arrangement.
Experiments that would have been dangerous to life and limb had we
tried them with a paper nest hanging in the open, were easy here so
long as we kept calm and unflurried. Intent upon their own affairs,
and unsuspicious of evil, perhaps because they knew themselves to
be armed against aggression, they accepted our presence, at first
with indifference; but as we sat there day after day we must have
become landmarks to them, and perhaps before the summer was over they
considered us really a part of home.
[Illustration: WASP EATING]
While poor humanity takes comfort in a mid–day siesta, wasps love the
heat of noontide, and with every rise in temperature they fly faster,
hum louder, and rejoice more and more in the fullness of life. The
entrance to the Vespa nest was but an inch across; and once when they
were going in and out in a hurrying throng, jostling each other in
their eagerness, we counted the number that passed, one taking the
entrances and one the exits. In ten minutes five hundred and ninety–two
left the nest and two hundred and forty–seven went in, so that we saw
eight hundred and thirty–nine or about eighty to the minute. This must
be a strong swarm, wonderful indeed when we thought that it had all
come from a single queen mother. We imagined how she had made an early
start, digging a hole in the ground, building within it a paper comb
with five or six cells around a central column, and laying therein
some neuter eggs; how she had then spent a month in attending carefully
to the beginnings of things, feeding the young larvæ as they hatched,
and watching over them through their childhood and youth; and then how
her solicitude was rewarded by the filial devotion with which this
first set of workers took upon themselves the labor of excavating,
building, and feeding the young, everything indeed except the
egg–laying. These queens, surrounded though they are by respectful and
attentive subjects, have much the worst of it in our estimation, never
going out, and passing their lives in a dull routine. Through the early
summer only neuters are produced, but when fall approaches the future
generation is provided for by the development of males and females. The
activity of the little colony is limited by the season, for as the days
grow colder the males and females leave the nest and mate, and a little
later both males and workers lose ambition, become inactive and finally
die, while the queens hide away in protected corners to reappear in the
spring. The eggs and larvæ, left unfed and uncared for, become a prey
to moulds and to hordes of insects, and thus the swarm comes to an end.
We had once made some not very successful attempts to find out whether
spiders had a sense of color; and seeing that the conditions were
much more favorable with our present subjects, we thought it would be
a good plan to test their knowledge of the spectrum. Providing six
sheets of stiff paper two feet square, colored respectively red, blue,
green, pink, and two shades of yellow, and cutting a circular hole four
and one half inches in diameter in the centre of each, we began our
experiments by placing the red paper over the nest so that the entrance
was clearly exposed. The outgoing wasps dashed upward without noticing
it, but great was the confusion among the homecomers. Thrown out of
their reckoning, they clamored about us in ever increasing swarms. Like
Homer’s wasps,
“All rise in arms and with a general cry
Assert their domes and buzzing progeny,”
and a crisis (for us) was approaching, when one, a pioneer of thought,
determined to go into the hole, which did not look like the right hole,
although it was where the right hole ought to be; and so potent is
example that one by one the others followed. Three hours later they had
become accustomed to the change, and went in and out as usual.
They had noticed the paper; that was plain enough, but did they notice
the redness? To test this, we left things as they were for two days,
and then substituted blue paper for the red. Again the confusion, the
swarming of fervent legions, the noisy expostulations, the descent of
one after another; but this time they settled down to their ordinary
routine in a little more than two hours. On the following day we
removed the blue paper, leaving the grass around the nest exposed;
and this proved a new source of mystification, but not so serious as
the others. At the end of an hour twenty–five or thirty were still
buzzing about, needing the guidance of the blue paper to get inside,
and entering at once when it was replaced. As we tried new colors
from day to day a few of the wasps became entirely reconciled to our
interference, and paid no attention to the changes, while the others
grew more or less accustomed to the idea of mutability, and were but
little disturbed, although they still showed their consciousness of
each alteration by making a few circles before going in. We once placed
some dark red nasturtiums on light yellow paper near the nest, and
found that more than one third of the homecoming wasps flew to them
and hovered over them before entering. When light yellow nasturtiums,
nearly matching the paper in color, were substituted, only one out of
thirty–six noticed them; and as the odor was as strong in one case as
the other, it would seem that the color was the attracting force.
Our final color experiment was to let the blue paper remain for a day
or two, giving time for all the wasps to become familiar with it, and
then to leave it on the ground a foot and a half away, while replacing
it with yellow. This gave a false nest surrounded by the color that
they had been associating with the entrance, and a true nest surrounded
by a new color. In the next ten minutes two hundred and seventy wasps
came home, and every one of them went to the false nest. Many circled
above it, others entered the hole in the paper, and some began to
excavate, and made quite a depression in the ground; but gradually they
found their way home. Three hours later seventy–six wasps entered the
false nest in five minutes, and at evening they were still visiting
it in goodly numbers; but on the next day we saw only two that were
deceived.
On successive days we substituted red for yellow, green for red, and
so on, always with similar results, although the wasps became more and
more accustomed to the vicissitudes of their life, and after a time
seemed to look for the hole itself without relying upon the color to
guide them. They found their nest under a color new to them much more
readily than when the paper was taken entirely away and the ground
left exposed. Once when the green paper was around their nest, and the
wind blew it over the hole so that they could not enter, at least
one hundred collected, many of them settling in the false nest; when
we lifted the green paper, leaving the hole free, only three or four
entered, but when we put it back in place they rushed in six or seven
at a time. It was plainly the color that directed them.
This was a nearly rainless summer,—a condition extremely favorable
to wasp development. Nests multiplied and grew until the whole
country–side complained, and no wonder, for houses were full of them,
and at mealtimes they gathered at the table with the members of the
family. How did they know when dinner was ready? It could not have been
by the sight, unfamiliar to them, of cooked food; was it, then, through
the sense of smell?
Many were the questions that we asked in vain of our Vespas, but here
was one that they could readily be made to answer. We rolled up two
bundles, one of nothing but gauze, and another, like it in appearance,
but containing some warm chicken bones; these were laid to one side of
the nest, the color of the gauze matching that of the paper on which
it was placed. The wasps in returning to the nest, even though loaded
with food, could not resist the appetizing odor, and settled thickly
upon the bone bundle, trying their best to penetrate within, while
the empty gauze was unnoticed. As the bones grew cold and dry they
attracted less attention, but two days later they were occasionally
visited.
Having killed two wasps that had alighted on the ground, by striking
them with a folded paper, we took them up and placed one of them at a
distance, so that it was entirely hidden in the grass. Five settled
above it, and after they had carried it away the place was visited by
several others, while the spot upon which we had killed them drew to it
nine wasps within fifteen minutes. Thus they seemed very keen of scent
where animal matter was concerned; but the powerful oils of peppermint
and wintergreen, although noticed, aroused little attention, perhaps
because they indicated nothing of interest to them.
Our experiments on hearing met with negative results. The wasps seemed
insensible to any noise we could make or that we could produce by
whistles of various degrees of shrillness. This of course does not show
that they cannot hear, and any one who has been unfortunate enough to
disturb them in the neighborhood of their nest will remember how their
angry buzzing seemed to serve as a battle cry to gather all the members
of the clan for the attack.
Our Vespas began to work an hour or two after sunrise, and did not stop
until dusk. One cloudy evening when darkness fell early they continued
to return to the nest, being able to fly to the right spot without any
hesitation, although our vision did not permit us to see the opening
without going down on our knees and looking closely. At last it grew
perfectly dark, and we stuffed a handkerchief into the hole, with the
result that seventy–five, coming home without a ray of light to guide
them, were shut out, and were found clustered about the spot on the
following morning.
We wanted to estimate the amount of labor done by a worker in a day,
and so, rising one morning at the first bird call, we went out into the
freshness of dawn, and for an hour had the world to ourselves; but a
little before five a few straggling wasps that had stayed out all night
began to bring in loads, and by half past seven they were fairly under
way. From half past four until twelve we counted all that passed, 4534
going out and 3362 coming home; and with all this activity there seemed
to be no pleasure excursions, for each one carried food when returning,
and took out a pellet of earth when leaving. We once raised a little
garden from the pellets that were dropped on our porch table where we
kept a bowl of water. Wasps are great drinkers, and when they find
such a provision they come frequently to refresh themselves, dropping
their loads as they alight. This habit of holding on to their loads
until they settle down may perhaps make them a factor in extending the
boundaries of plant distribution, both under ordinary conditions and
when, as must often happen with little creatures flying so high, they
are blown to long distances from home.
[Illustration: PAPER NEST WITH SIDE REMOVED TO SHOW CONSTRUCTION OF
COMBS]
Having kept close track not only of the numbers, but of the hours,
each count being made to cover five minutes, we were able to calculate
that an average trip occupied forty–three minutes. When we met these
wasps in the garden they never seemed to be hurrying, and had the air
of amusing themselves; but they must be faithful workers to accomplish
so much. The curious fact has been established that when food is very
plentiful the workers begin to lay male eggs, thus taking from the
queen a part of her burden and leaving her free to produce neuters and
females. The nest that we were watching was found, at the end of the
season, to contain 4661 wasps in various stages of development, and
others that we opened had from two to four thousand. This is nothing to
the social wasps of China, where a single household is made up of from
fifteen to twenty thousand members; but China is a thickly populated
country, and perhaps with wasps as with human beings several families
live in a single domicile.
Outside of their wonderful social instincts our wasps are found wanting
in the higher gifts of emotion and intellect. When we killed a number
of them and placed them near the nest, their nearest relatives wasted
no time in mourning, nor yet in revenge, but calmly cut up the bodies
and fed them to the ever hungry young ones. If we placed some rich and
tempting morsels at a distance, two or three would discover them, and
would go back and forth all day without telling the others about it, as
ants would have done under like circumstances. When we obstructed the
opening to their nest by lightly laying blades of grass across, the day
passed without its occurring to the wasps to lift them away, although
they suffered the greatest inconvenience in getting in and out,
crawling laboriously through, and in some instances giving up the task
and flying away.
Vespa maculata, building on trees and fences, has practically the
same habits as the ground wasp, germanica, the internal structure
of the nest following the same plan, while the outer wall is of a
papery substance like that of the combs, made from the scrapings of
weather–beaten wood. The genus Polistes builds combs similar to that of
Vespa, under porches or in any sheltered place, and does not inclose
them. All these wasps, when adult, enjoy fruit and flowers as well
as animal food; but only this last is used for the young, and many a
caterpillar creeping along with sinister design is snatched by them to
be chewed into a pulpy mass, and then fed to the larvæ. No calculation
has been made of the value of these wasps in agriculture, and one
of the things that farmers have yet to learn is to encourage their
presence in orchards and gardens.
Some species are said to sting the drones and larvæ to death at the
close of the season, but this habit is not followed by V. germanica
and V. maculata. Since there is no store of provision to be economized
through the winter the only object of such conduct would be the
merciful one of ending their sufferings at once instead of letting them
perish by slow starvation, and we find no evidence for such elevated
ideas. What makes for the welfare of the species they thoroughly attend
to, but beyond that point they do not go.
The socialism of wasps is in a less evolved state than that of bees and
ants, and yet there is in it sufficient sacrifice of self to the common
good to excite the respectful wonder of human beings, whose relations
to each other and to the state have such different standards.
Chapter II
AMMOPHILA AND HER CATERPILLARS
BEFORE we had worked long on our Vespa family we were beguiled by
tempting opportunities into running after the solitary wasps. The
solitaries, so far as species are concerned, are immensely more
numerous than the socials; but they have only two sexes, and the males
and females usually see but little of each other after the mating
is over, although we occasionally find them living happily together
until the end of the season. In the early summer they begin to emerge
from the nest in which the eggs were laid the year before. Solitary
indeed they come into the world, the generation that gave them birth
having perished in the fall. For a time their career is one of unmixed
pleasure, and yet, free and unguided though they are, basking in the
sunshine, feeding on the flowers, or sleeping at night under some
sheltering leaf, they are hourly acquiring experience, so that when
the cares of life descend upon them they are no longer creatures
of mere instinct. With these sobering cares an almost absurdly
heavy sense of responsibility for future generations transforms the
hitherto happy–go–lucky females into grown–up wasps with serious views
on marketing and infant foods. Each one makes a separate nest and
provisions it by her own labor; and in many cases a new nest is made
for each egg. There is no coöperation among them; although in certain
genera, as Aphilanthops and Bembex, a number of individuals build
close together, forming a colony. The nests may be made of mud, and
attached for shelter under leaves, rocks, or eaves of buildings, or
may be burrows hollowed out in the ground, in trees or in the stems of
plants. The adult wasp lives upon fruit or nectar, but the young grub
or larva must have animal food; and here the parent wasp shows a rigid
conservatism, each species providing the sort of food that has been
approved by its family for generations, one taking flies, another bugs,
and another beetles, caterpillars, grasshoppers, crickets, locusts,
spiders, cockroaches, aphides, or other creatures, as the case may be.
When the egg–laying time arrives the female secures her prey, which
she either kills or paralyzes, places it in the nest, lays the egg
upon it, and then, in most cases, closes the hole and takes no further
interest in it, going on to make new nests from day to day. In some
genera the female maintains a longer connection with her offspring,
not bringing all the provision at once, but returning to feed the larva
as it grows, and leaving the nest permanently only when the grub has
spun its cocoon. The males never acquire this interest, so admirable
for the development of character, and aid little, if at all, in the
care of the family. The egg develops in from one to three days into a
footless, maggot–like creature which feeds upon the store provided for
it, increasing rapidly in size, and entering the pupal stage in from
three days to two weeks. In the cocoon it passes through its final
metamorphosis, emerging as a perfect insect, perhaps in two or three
weeks, or, in many cases, after the winter months have passed and
summer has come again.
Most graceful and attractive of all the wasps—“_taille effilée,
tournure svelte_,” as Fabre describes them, the Ammophiles, of all the
inhabitants of the garden, hold the first place in our affections.
Not so beautiful as the blue Pelopæus, nor so industrious as the
little red–girdled Trypoxylon, their intelligence, their distinct
individuality, and their obliging tolerance of our society make
them an unfailing source of interest. They are, moreover, the most
remarkable of all genera in their stinging habits, being supposed to
use the nicest surgical skill in paralyzing their caterpillars; and few
things have given us deeper pleasure than our success in following
the activities and penetrating the secrets of their lives. In our
garden we have two species of Ammophila, urnaria Cresson, and gracilis
Cresson, both of them being very slender–bodied wasps of about an inch
in length, gracilis all black, and urnaria with a red band around
the front end of the abdomen. A. polita and A. vulgaris, which look
much like urnaria, are common in the sandy fields west and south of
Milwaukee.
[Illustration: AMMOPHILA URNARIA CARRYING CATERPILLAR TO NEST]
During the earlier part of the summer we had often seen these wasps
feeding upon the nectar of flowers, especially upon that of the sorrel,
of which they are particularly fond; but at that time we gave them but
passing notice. One bright morning, however, we came upon an urnaria
that was so evidently hunting, and hunting in earnest, that we gave up
everything else to follow her. The ground was covered, more or less
thickly, with patches of purslain, and it was under these weeds that
our Ammophila was eagerly searching for her prey. After thoroughly
investigating one plant she would pass to another, running three or
four steps and then bounding as though she were made of thistledown and
were too light to remain upon the ground. We followed her easily, and
as she was in full view nearly all of the time we had every hope of
witnessing the capture; but in this we were destined to disappointment.
We had been in attendance on her for about a quarter of an hour when,
after disappearing for a few moments under the thick purslain leaves,
she came out with a green caterpillar. We had missed the wonderful
sight of the paralyzer at work; but we had no time to bemoan our loss,
for she was making off at so rapid a pace that we were well occupied in
keeping up with her. She hurried along with the same motion as before,
unembarrassed by the weight of her victim. For sixty feet she kept to
open ground, passing between two rows of bushes; but at the end of this
division of the garden, she plunged, very much to our dismay, into a
field of standing corn. Here we had great difficulty in following her,
since, far from keeping to her former orderly course, she zigzagged
among the plants in the most bewildering fashion, although keeping a
general direction of northeast. It seemed quite impossible that she
could know where she was going. The corn rose to a height of six feet
all around us; the ground was uniform in appearance, and, to our eyes,
each group of cornstalks was just like every other group, and yet,
without pause or hesitation, the little creature passed quickly along,
as we might through the familiar streets of our native town.
At last she paused and laid her burden down. Ah! the power that has led
her is not a blind, mechanically perfect instinct, for she has traveled
a little too far. She must go back one row into the open space that she
has already crossed, although not just at this point. Nothing like a
nest is visible to us; the surface of the ground looks all alike, and
it is with exclamations of wonder that we see our little guide lift two
pellets of earth which have served as a covering to a small opening
running down into the ground.
The way being thus prepared, she hurries back with her wings quivering
and her whole manner betokening joyful triumph at the completion of
her task. We, in the mean time, have become as much excited over the
matter as she is herself. She picks up the caterpillar, brings it to
the mouth of the burrow, and lays it down. Then, backing in herself,
she catches it in her mandibles and drags it out of sight, leaving us
full of admiration and delight.
How clear and accurate must be the observing powers of these wonderful
little creatures! Every patch of ground must, for them, have its own
character; a pebble here, a larger stone there, a trifling tuft of
grass—these must be their landmarks. And the wonder of it is that their
interest in each nest is so temporary. A burrow is dug, provisioned and
closed up, all in two or three days, and then another is made in a new
place with everything to learn over again.
From this time on to the first of September our garden was full of
these wasps, and they never lost their fascination for us; although,
owing to a decided difference between their taste and ours as to what
constituted pleasant weather, all our knowledge of them was gained by
the sweat of our brows. When we wished to utilize the cool hours of
the morning or of the late afternoon in studying them, or thought to
take advantage of a cloud which cast a grateful shade over the sun at
noonday, where were our Ammophiles? Out of sight entirely, or at best
only to be seen idling about on the flowers of the onion or sorrel. At
such a time they seemed to have no mission in life and no idea of duty.
But when the air was clear and bright and the mercury rose higher and
higher, all was changed. Their favorite working hours were from eleven
in the morning to three in the afternoon, and when they did work they
threw their whole souls into it. It was well that it was so, for they
certainly needed all the enthusiasm and perseverance that they could
muster for such wearisome and disappointing labor. Hour after hour was
passed in search, and often there was nothing to show at the end of
it. Urnaria hunted on bare ground, on the purslain, and most of all
on the bean–plants. These were examined carefully, the wasp going up
and down the stems and looking under every leaf; but the search was so
frequently unsuccessful that in estimating their work we are inclined
to think that they can scarcely average one caterpillar a day.
In this species, as in every one that we have studied, we have found a
most interesting variation among the different individuals, not only in
methods, but in character and intellect. While one was beguiled from
her hunting by every sorrel blossom she passed, another stuck to her
work with indefatigable perseverance. While one stung her caterpillar
so carelessly and made her nest in so shiftless a way that her young
could survive only through some lucky chance, another devoted herself
to these duties not only with conscientious thoroughness, but with an
apparent craving after artistic perfection that was touching to see.
The method employed by the Ammophiles in stinging their prey is more
complex than that of any other predatory wasp. The larvæ with which
they provision their nests are made up of thirteen segments, and
each of these has its own nervous centre or ganglion. Hence if the
caterpillar is to be reduced to a state of immobility, or to a state
so nearly approaching immobility that the egg may be safely laid upon
it, a single sting, such as is given by some of the Pompilidæ to their
captured spiders, will be scarcely sufficient. All this we knew from
Fabre’s “Souvenirs,” and yet we were not at all prepared to believe
that any plain American wasp could supply us with such a thrilling
performance as that of the Gallic hirsuta, which he so dramatically
describes. We were, however, most anxious to be present at the
all–important moment that we might see for ourselves just how and where
urnaria stings her victim.
For a whole week of scorching summer weather we lived in the bean
patch, scorning fatigue. We quoted to each other the example of
Fabre’s daughter Claire, who followed Odynerus with unfaltering zeal
until a sunstroke laid her low. We attended scores of wasps as they
hunted; we ran, we threw ourselves upon the ground, we scrambled along
on our hands and knees in our desperate endeavors to keep them in
view, sometimes with our eyes upon the wasps themselves and sometimes
pursuing their shadows, which, like those of coming events, were cast
before; and yet they escaped us. After we had kept one in sight for an
hour or more, some sudden flight would carry her far away, and all our
labor was lost.
At last, however, our day came. We were doing a little hunting on our
own account, hoping to find some larvæ which we could drop in view of
the wasps and thus lead them to display their powers, when we saw an
urnaria fly up from the ground to the underside of a bean leaf and
knock down a small green caterpillar. Breathless with an excitement
which will be understood by those who have tasted the joy of such a
moment, we hung over the actors in our little drama. The ground was
bare, we were close by and could see every motion distinctly. Nothing
more perfect could have been desired.
The wasp attacked at once, but was rudely repulsed, the caterpillar
rolling and unrolling itself rapidly and with the most violent
contortions of the whole body. Again and again its adversary descended,
but failed to gain a hold. The caterpillar, in its struggles, flung
itself here and there over the ground, and had there been any grass
or other covering near by it might have reached a place of partial
safety; but there was no shelter within reach, and at the fifth attack
the wasp succeeded in alighting over it, near the anterior end, and in
grasping its body firmly in her mandibles. Standing high on her long
legs and disregarding the continued struggles of her victim, she lifted
it from the ground, curved the end of her abdomen under its body, and
darted her sting between the third and fourth segments. From this
instant there was a complete cessation of movement on the part of the
unfortunate caterpillar. Limp and helpless, it could offer no further
opposition to the will of its conqueror. For some moments the wasp
remained motionless, and then, withdrawing her sting, she plunged it
successively between the third and the second, and between the second
and the first segments.
The caterpillar was now left lying on the ground. For a moment the wasp
circled above it, and then, descending, seized it again, further back
this time, and with great deliberation and nicety of action gave it
four more stings, beginning between the ninth and tenth segments and
progressing backward.
Urnaria, probably feeling—as we certainly did—a reaction from the
strain of the last few minutes, and a relief at the completion of her
task, now rested from her labors. Alighting on the ground close by, she
proceeded to smooth her body with her long hind legs, standing, in the
mean time, almost on her head, with her abdomen directed upward. She
then gave her face a thorough washing and rubbing with her first legs,
and not until she had made a complete and satisfactory toilet did she
return to the caterpillar.
We saw Ammophila capture her prey only three times during the whole
summer; but from these observations and from the condition of her
caterpillars taken at various times from nests, her method seems to be
wonderfully close to that of hirsuta, with just about the same amount
of variation in different individuals.
Thus in our second example, she stung the first three segments in
the regular order, the third, the second, and lastly (and most
persistently) the first. She then went on, without a pause, to sting
the fourth, fifth, sixth, and seventh, stopping at this point and
leaving the posterior segments untouched. In our first example, it will
be remembered, the middle segments were spared. The stinging being
completed, she proceeded to the process known as _malaxation_, which
consists in repeatedly squeezing the neck of the caterpillar, or other
victim, between the mandibles, the subject of the treatment being
turned around and around so that all sides may be equally affected.
[Illustration: AMMOPHILA URNARIA STINGING CATERPILLAR]
In our third case a caterpillar which we had caught was placed in front
of a wasp just after she had carried the second larva into her nest.
She seemed rather indifferent to it, passing it once or twice as she
ran about, but finally picked it up and gave it one prolonged sting
between the third and fourth segments. She then spent a long time in
squeezing the neck, pinching it again and again, after which it was
left on the ground; and as she showed no further interest in it we
carried it home for further study.
In the three captures, then, that came under our observation, all
the caterpillars being of the same species and almost exactly of the
same size, three different methods were employed. In the first, seven
stings were given at the extremities, the middle segments being left
untouched, and no malaxation was practiced. In the second, seven
stings again, but given in the anterior and middle segments, followed
by slight malaxation. In the third, only one sting was given, but the
malaxation was prolonged and severe.
Let us now compare these variations with those of Fabre. In his first
case the sting entered at twelve different points, beginning between
the first and second segments and progressing regularly backward. There
was no malaxation. In his second example the third, second, and first
segments were stung in the order given, and thereafter each succeeding
segment up to the ninth, nine stings being given in all, with careful
malaxation following. In his later experiments, which seem to have been
numerous, he found that as a usual thing all the segments were stung,
although the posterior three or four were occasionally spared, but that
the order in which they were operated upon, as well as the amount of
malaxation, was very variable.
Our conclusions, then, as to Ammophila’s methods of stinging agree
fairly well with those of Fabre; but there is one important exception.
In his cases the middle segments, upon one of which the egg is laid
in our species as well as in his, were invariably stung, and this he
considers a point of extreme importance. In one of our cases the middle
segments were not touched.
[Illustration: CATERPILLAR WITH EGG OF AMMOPHILA URNARIA]
The point in which our observations differ most widely from those of
Fabre is in the condition of the caterpillars after the stinging.
He seems to have found that they always lived a long time, but in a
motionless or nearly motionless state; and he dwells at length upon the
necessity of both of these conditions, since he believes that while the
wasp larva must have perfectly fresh food, any violent motion would
imperil its safety. As a matter of fact we found a wide variation in
the thoroughness with which the wasps performed their task. We had, in
all, fifteen caterpillars upon which urnaria had worked her will; and
while a few of them fulfilled to a nicety the conditions which Fabre
believes to be imperative, most of them were far from doing so. Some
of them lived only three days, others a little longer, while still
others showed signs of life at the end of two weeks. Urnaria stores
two caterpillars, and in more than one instance the second one died
and became discolored before the first one was entirely eaten. The
wasp larva did not, as might have been expected, find fault with this
arrangement, but proceeded to attack number two with good appetite, ate
it all up, and then spun its cocoon as though nothing unpleasant had
occurred.
The second condition was also violated. In one case the bite of the
newly hatched larva caused the caterpillar to rear upon end in so
violent a manner that it looked as though the little creature would
surely be dislodged. Another caterpillar kept up a continuous wriggling
without any external stimulation, and when it was touched it rolled
about almost as these larvæ do in a healthy state, and yet the egg was
not shaken off. The caterpillar which received but a single sting,
although not motionless, would have been a safer repository for the egg
than either of these. Others fulfilled Fabre’s condition perfectly,
lying immovable except when stimulated, and then responding only by a
slight quivering of the legs or skin.
Among the fifteen caterpillars that we have taken from the nests of
urnaria three kinds are represented, twelve of them belonging to one
species, two to the second, and one to the third.
The egg, which is laid upon the side of the sixth or seventh segment,
hatches in from two to three days; the larva spends from six days to
two weeks in eating, and then spins its pale yellowish cocoon.
[Illustration: NEST OF AMMOPHILA]
The nesting habits of urnaria closely resemble those of the other
members of the genus, as reported by various observers. The spot chosen
is in firm soil, sometimes in open ground, but much more frequently
under the leaves of some plant. The plan is a very simple one. A
tunnel of about an inch in length leads to the pocket in which the
caterpillars are stored. There is no hardening of the walls in any
part. We took pains to draw every nest that we opened, and there was a
very considerable variation in the minor details, such as the obliquity
of the entrance tunnel, the shape of the pocket, and the angle at
which the tunnel and pocket were joined.
The work is done with the mandibles and the first legs. When it has
proceeded so far that the wasp is partly hidden, she begins to carry
the earth away from the nest. In doing this she backs up to the edge
of the opening and, flying a little way, gives a sort of flirt which
throws the pellet that she carries in her mandibles to a distance. She
then alights where she is and pauses a moment before she runs back
to the hole, or, in some cases, darts back on the wing. We watched
the process of nest–making five times during the summer. In the first
instance Ammophila, having made her excavation, ran off and after some
search returned with a good–sized lump of earth. This she laid over
the opening, which was now entirely hidden. She then flew to the bean
patch close by, but after ten minutes she came back and looked at her
nest. It was so neatly covered as to be almost indistinguishable, but
to this fastidious little creature something seemed lacking. She pulled
away the cover, carried out three or four more loads, and then began to
search for another piece for closing. After a time she came hurrying
back with a lump of earth, but when close to the nest she concluded
that it would not do, dropped it, and ran off in another direction.
Presently she found one which fitted into the hole exactly, and after
placing it she brought a much smaller piece which she put above and to
one side. She then stood back and surveyed the whole, and it seemed to
us that we could read pride and satisfaction in her mien. She then flew
away, and we supposed that that stage of the work was completed. Upon
coming back two hours later, however, we found that she had been trying
some more improvements, as a number of little pellets had been piled
up over the nest. This wasp, by the way, never succeeded in finding a
caterpillar, since when we opened the burrow a few days later it was
still empty. Perhaps she came to some untimely end.
Of the other wasps that we saw making a temporary closure of their
nests, one wedged a good–sized stone deep down into the neck of the
burrow and then filled the space above, solidly, with smaller stones
and earth. Another placed two lumps of earth just below the surface
of the ground, filled the opening with pellets loosely thrown in, and
then kicked some light dust over the whole. The others used only two or
three lumps of earth, which they fitted neatly into the opening just
below the surface. Although it is usual for urnaria to leave her nest
closed while she is off searching for her prey, there is no invariable
rule in the matter, even for single individuals. Once having seen a
wasp dig her nest and close it up, we drew some radiating lines from
the spot, in the light dust that covered the place, that we might find
it again. When we returned, two hours later, the same wasp had made a
nest four or five inches distant from the first one, and had left it
wide open, while she had gone off to search for her caterpillar. She
had probably been alarmed by the marks that we had made, and had felt
it necessary to dig a new nest, but being in a hurry to lay her egg had
omitted the usual process of closing it. We witnessed the storing of
the caterpillar and the final closing.
From Fabre we learn that argentata and sabulosa close the nest as soon
as it has been made, at least when the provisioning is to be postponed
until the next day, while holosericea leaves it open until it is
completely stored. He suggests an explanation for this variation by
dwelling upon the inconvenience that would result if it were opened
every time that the wasp brought in a caterpillar, since holosericea
stores up five or six small larvæ instead of one or two large ones. But
what, then, shall be said of polita and yarrowii, which, while they
also store a number of small caterpillars, take pains to close and
conceal the entrance every time they come out? We see the same habit
in other genera where the mother continually passes in and out, as in
Bembex and Oxybelus.
Fabre thinks that hirsuta has the habit, unusual for Ammophila, of
catching her prey first and then digging the hole in which she bestows
it. As she takes only one large caterpillar she is thus relieved of the
necessity of closing the nest more than once.
As has been said, urnaria usually hunts a long time before she finds
her caterpillar, and one or two days may pass before anything is put
into the nest. During this prolonged search she often revisits the
spot, and thus keeps fresh the memory of its locality. As soon as the
first caterpillar is stored she lays an egg on it, and then closes the
nest as before. The second one may be brought in within a few hours;
but in one instance that came under our notice we feel sure that the
interval was as much as three days. We saw the interment of the second
caterpillar, and upon excavating, found on the first one a larva at
least a day old; we suppose that at least two days had elapsed between
the laying and the hatching of the egg.
When the provisioning is completed the time arrives for the final
closing of the nest; and in this, as in all the processes of Ammophila,
the character of the work differs with the individual. For example, of
two wasps that we saw close their nests on the same day, one wedged
two or three pellets into the top of the hole, kicked in a little
dust, and then smoothed the surface over, finishing it all within five
minutes. This one seemed possessed by a spirit of hurry and bustle, and
did not believe in spending time on non–essentials. The other, on the
contrary, was an artist, an idealist. She worked for an hour, first
filling the neck of the burrow with fine earth which was jammed down
with much energy,—this part of the work being accompanied by a loud and
cheerful humming,—and next arranging the surface of the ground with
scrupulous care, and sweeping every particle of dust to a distance.
Even then she was not satisfied, but went scampering around, hunting
for some fitting object to crown the whole. First she tried to drag a
withered leaf to the spot, but the long stem stuck in the ground and
embarrassed her. Relinquishing this, she ran along a branch of the
plant under which she was working and, leaning over, picked up from the
ground below a good–sized stone; but the effort was too much for her,
and she turned a somersault on to the ground. She then started to bring
a large lump of earth; but this evidently did not come up to her ideal,
for she dropped it after a moment, and seizing another dry leaf carried
it successfully to the spot and placed it directly over the nest. A
third instance of the final closing of the nest was intermediate
between these two, the work occupying twenty minutes. The wasp first
put a plug well down, then dropped in several large pellets, brushed in
a quantity of fine earth, and finally smoothed the surface over.
We had another much less worthy example, one, indeed, that went to
the extreme of carelessness. We first saw her in the morning carrying
her caterpillar across the field. She frequently dropped it and ran
or flew to a little distance, and when she took it again the venter
was sometimes up and sometimes down, whichever way it happened. Her
nest was a very poor affair just beneath the surface, and after the
caterpillar was carried in, it was visible from above. She filled the
hole with loose particles of earth and then scratched the surface of
the ground a little in a perfunctory sort of way, as different as
possible from the painstaking labor that we had been accustomed to
in her sisters. That afternoon we opened the nest and removed its
contents. The next morning we saw this wasp bringing home her second
caterpillar. She was much puzzled and disturbed at the destruction
of her nest, and hunted for it for an hour and a half, leaving the
caterpillar on the ground near by. We could not help feeling sorry that
we had interrupted the contented routine of her life. She finally gave
up in despair, and we took possession of the deserted caterpillar.
Just here must be told the story of one little wasp whose individuality
stands out in our minds more distinctly than that of any of the others.
We remember her as the most fastidious and perfect little worker
of the whole season, so nice was she in her adaptation of means to
ends, so busy and contented in her labor of love, and so pretty in
her pride over the completed work. In filling up her nest she put her
head down into it and bit away the loose earth from the sides, letting
it fall to the bottom of the burrow, and then, after a quantity had
accumulated, jammed it down with her head. Earth was then brought from
the outside and pressed in, and then more was bitten from the sides.
When, at last, the filling was level with the ground, she brought a
quantity of fine grains of dirt to the spot, and picking up a small
pebble in her mandibles, used it as a hammer in pounding them down
with rapid strokes, thus making this spot as hard and firm as the
surrounding surface. Before we could recover from our astonishment at
this performance she had dropped her stone and was bringing more earth.
We then threw ourselves down on the ground that not a motion might be
lost, and in a moment we saw her pick up the pebble and again pound
the earth into place with it, hammering now here and now there until
all was level. Once more the whole process was repeated, and then the
little creature, all unconscious of the commotion that she had aroused
in our minds,—unconscious, indeed, of our very existence and intent
only on doing her work and doing it well,—gave one final, comprehensive
glance around and flew away.
[Illustration: AMMOPHILA URNARIA USING STONE TO POUND DOWN EARTH OVER
NEST]
We are claiming a great deal for Ammophila when we say that she
improvised a tool and made intelligent use of it, for such actions are
rare even among the higher animals; but fortunately our observation
does not stand alone, although we supposed this to be the case at the
time that it was made. Some weeks later, seeing a note of a similar
occurrence by Dr. S. W. Williston, of Kansas University, we wrote to
him on the subject. In his reply he said that he had waited for a year
before venturing to publish his observation, fearing that so remarkable
a statement would not be credited. His account is so interesting that
we quote it at length.
Even the casual observer, to whom all insects are bugs, cannot help but
be struck by the great diversity and number of the fossorial Hymenoptera
of the plains. Water is often inaccessible, trees there are few or
none, and only in places is the vegetation at all abundant. A much
larger proportion of insects, hence, find it necessary to live or breed
in holes in the ground, than is the case in more favored localities.
Especially is this the case with the Hymenoptera, great numbers and many
species of which thus breed in excavations made by themselves.
While packing specimens on an open space, uncovered by buffalo grass,
in the extreme western part of Kansas, the early part of last July, the
attention of a friend and myself was attracted by the numerous wasps
that were constantly alighting upon the ground. The hard, smooth baked
surface showed no indications of disturbance, and it was not till we
had attentively watched the insects that we learned what they were
doing. The wasp is a very slender one, more than an inch in length,
with a slender, pedicellate abdomen; it is known to entomologists as
Ammophila yarrowii Cres. They were so numerous that one was distracted
by their very multiplicity, but, by singling out different individuals,
we were enabled to verify each detail of their operations. An insect,
alighting, ran about on the smooth, hard surface till it had found a
suitable spot to begin its excavation, which was made about a quarter
of an inch in diameter, nearly vertical, and carried to a depth of
about four inches, as was shown by opening a number of them. The earth,
as removed, was formed into a rounded pellet and carefully carried to
the neighboring grass and dropped. For the first half of an inch or so
the hole was made of a slightly greater diameter. When the excavation
had been carried to the required depth, the wasp, after a survey of
the premises, flying away, soon returned with a large pebble in its
mandibles, which it carefully deposited within the opening; then,
standing over the entrance upon her four posterior feet, she (I say
she, for it was evident that they were all females) rapidly and most
amusingly scraped the dust with her two front feet, “hand over hand,”
back beneath her, till she had filled the hole above the stone to the
top. The operation so far was remarkable enough, but the next procedure
was more so. When she had heaped up the dirt to her satisfaction, she
again flew away and immediately returned with a smaller pebble, perhaps
an eighth of an inch in diameter, and then standing more nearly erect,
with the front feet folded beneath her, she pressed down the dust all
over and about the opening, smoothing off the surface, and accompanying
the action with a peculiar rasping sound. After all this was done, and
she spent several minutes each time in thus stamping the earth so that
only a keen eye could detect any abrasion of the surface, she laid
aside the little pebble and flew away to be gone some minutes. Soon,
however, she comes back with a heavy flight, scarcely able to sustain
the soft green larva, as long as herself, that she brings. The larva
is laid upon the ground, a little to one side, when, going to the spot
where she had industriously labored, by a few, rapid strokes she throws
out the dust and withdraws the stone cover, laying it aside. Next,
the larva is dragged down the hole, where the wasp remains for a few
minutes, afterwards returning and closing up the entrance precisely as
before. This, we thought, was the end, and supposed that the wasp would
now be off about her other affairs, but not so; soon she returns with
another larva, precisely like the first, and the whole operation is
again repeated. And not only the second time, but again and again, till
four or five of the larvæ have been stored up for the sustainment of
her future offspring. Once, while a wasp had gone down the hole with a
larva, my friend quietly removed the door stone that she had placed by
the entrance. Returning, she looked about for her door, but not finding
it, apparently mistrusted the honesty of a neighbor, which had just
descended, leaving her own door temptingly near. She purloined this
pebble and was making off with it, when the rightful owner appeared and
gave chase, compelling her to relinquish it.
The things that struck us as most remarkable were the unerring judgment
in the selection of a pebble of precisely the right size to fit the
entrance, and the use of the small pebble in smoothing down and packing
the soil over the opening, together with the instinct that taught them
to remove every evidence that the earth had been disturbed.
Since the Ammophiles of our species make their nests first and then do
their hunting it follows that they must sometimes carry their prey for
a considerable distance. The most ambitious attempt of this kind that
we ever witnessed was made by gracilis.
The wasp was first seen carrying a large green caterpillar, which
projected at both ends beyond her own body, across the potato field at
the lower end of the garden. We could not tell how far she had already
brought it, but judging by the direction from which she was coming, and
by the fact that we had never seen that species of caterpillar in the
garden, she had probably come through the fence from the woods beyond.
She moved along briskly over the remaining part of the potato field,
and then through an adjoining bean patch into the corn field. This had
been a place of much anxiety to us earlier in the summer; but now the
corn had been stacked and we could follow her without difficulty. So
far she had been going due south; but now she made a turn and plunged
into the long, tangled grass which grew around and among some large,
overgrown raspberry bushes. To keep track of her here seemed a hopeless
task, but we resolved to do our best, and followed anxiously after.
The wasp worked her way along about two inches above the ground and
very much below the top of the grass, clinging to the blades with her
feet and making surprisingly good progress. When half way through
the raspberry bushes she carried the caterpillar up on to a branch,
deposited it there, and after circling about to take her bearings, flew
away, doubtless to visit her nest and to make sure that she was going
in the right direction.
We, ourselves, were very glad of the chance to rest our tired eyes
and nerves from the strain of following her. The journey, so far, had
occupied nearly an hour, at almost every instant of which it had been
exceedingly difficult to keep her in view. But for our united efforts
we should certainly have failed.
While standing guard over the caterpillar we noticed that it moved its
head from side to side, showing that the first segment could not have
been severely stung, as is usually the case in the work of urnaria.
In five minutes the wasp returned, and, with the air of feeling that
everything was right, picked up her burden and carried it laboriously
through the remaining bushes and then through the grassy space that
edged the garden, as far as the rail fence which separated this part
of the grounds from the woods. Without a pause she climbed on to this
fence to the height of the second rail, passed through, and flew down
on the further side. Here she paused a moment, perhaps to take breath,
and we looked at each other in some dismay. Whither was she leading us?
We had now been following her for over an hour, and she looked equal
to as much again as she started off once more, rapidly this time, for
the grass was short here and the traveling was easy. Soon, however,
it became evident that things were going wrong, although we could not
determine what was the matter. The caterpillar was laid down while the
wasp absented herself for six minutes. She returned and carried it for
fifteen minutes, and then left it for half an hour. Once more she came
back, and carried it for ten minutes, and then she flew away. It was
now four o’clock, and we had been following her since two. We watched
over the caterpillar for an hour longer, but saw no more of the wasp.
Did she become discouraged at the magnitude of her task? It would have
been a thousand times easier for her to have dug her nest close by the
place of capture, but perhaps she had one larva already stored with her
egg upon it. The caterpillar was carried two hundred and sixty–one feet
while we watched her, with an unknown distance at each end to complete
the line between the place of capture and the nest. She could scarcely
have lost her way, since at every return she proceeded on her journey
in one general direction without any hesitation. It seems probable
then that she had hunted too far afield, and did not realize, when she
started with her booty, what an undertaking it would be to carry it to
the nest. We once saw A. vulgaris have a similar experience. She was
running along with a small green caterpillar, but became discouraged
either at the difficulty of finding her nest, or at the distance she
had to cover. She would carry the caterpillar a little way, drop it,
circle about a while, and then pick it up again; but finally she gave
up the whole undertaking and flew away.
The affairs of Ammophila must frequently go wrong, since in still
another of our few examples we saw much trouble and labor wasted. The
wasp, in this case an urnaria, captured her caterpillar successfully
and proceeded to carry it off. She was far from being in a hurry,
going along for a foot or so, and then making a long pause, during
which she would lay it down and either circle above it, perhaps to
take bearings, or spend the time in cleaning herself off, stroking and
smoothing every part of her body with the utmost care and deliberation.
Her stops were so frequent and so lengthy that nearly an hour was
occupied in going about twenty–five feet. When, at last, the nest was
reached, the plug was removed from the entrance and the caterpillar
dragged in, but almost immediately the wasp came out backwards with the
point of an egg projecting from the extremity of her abdomen. She ran
around and around the nest in a distracted way four or five times and
then went back, dragged the caterpillar out, and carried it away. The
egg came out further and further, and finally dropped on the ground
and was lost. The wasp, carrying the caterpillar, led us a long dance,
in a great semicircle over the field, coming back to the nest at last.
Instead of going in, however, she was about to start off on another
tour when we took her prey from her and placed it in the nest. The wasp
remained in the neighborhood for over an hour, but finally disappeared.
The nest was not closed, and when we dug it up on the following day it
contained only the caterpillar that we had put in.
We could usually enter into the feelings of the Ammophiles and
understand the meaning of their actions; but we were puzzled once,
when we saw an urnaria that had stored her second caterpillar and
closed her nest permanently, spend the rest of her morning in hunting.
Why in hunting? She had not dug a nest, she could not lay another egg
at once, she did not want a caterpillar, for when we offered her one
she stung it and then left it lying on the ground. The sun was bright,
the sorrel–blossoms invited her. Surely it would have been the part of
a rational wasp to have passed the rest of the day in feasting and fun.
We have said that urnaria stores two caterpillars, but this rule is
not without its exception. It was on the last day of the summer that
on a visit to our dear and fruitful potato field, we came upon a wasp
of almost double the ordinary size, that made, when flying, a loud hum
that at once attracted attention. She was just completing and closing
her nest, and we determined to watch and see what kind of a victim she
would bring in, as it seemed improbable that this great creature would
content herself with the ordinary fare of the species. The opening to
the nest measured half an inch in diameter.
It was eleven o’clock when she flew away. At half past twelve she
reappeared, coming from the direction of the woods, opened her nest,
and took out a few more pellets. Then she flew to a bush which grew
against the fence, three feet away, and following her quickly we saw
an immense green caterpillar placed high up on a branch. It must have
taken both strength and perseverance to lift this heavy weight so far
from the ground. She seized it at once and carried it down, not flying,
as these wasps sometimes do when they are descending with a burden, and
then dragged it into her nest, where it fitted rather tightly. This
nest was so shallow and so obliquely directed that the caterpillar was
plainly visible after it had been taken in.
After she had laid her egg she crawled out, getting past the
caterpillar with some difficulty, and closed the nest. There was
certainly no room for any further store of provisions, and from the
size of the caterpillar we judged that it would furnish sufficient
nourishment even for the offspring of this wasp. We were, therefore,
not surprised, upon opening the nest two days later, to find that
nothing more had been brought. We have said that the wasp larvæ spend
from six days to two weeks in eating. To be more exact, all that we
watched, with the exception of the one which developed from the egg
of this big creature, ate from six to eight days and then spun their
cocoons; but this one seemed determined to reach the size of its
mother, and ate continuously for fourteen days. Of course long before
this time had expired the remnant of the caterpillar had become a dry,
dark–colored mass which looked little likely to tempt the appetite, but
the great larva ate away with unabated relish, gradually acquiring the
color and almost the thickness of the caterpillar it had destroyed.
Ammophila polita, which we have never seen in the country, is very
common in the sandy fields to the south of Milwaukee. On the tenth of
September, in bright clear weather, we found half a dozen individuals
working within a few rods of each other, their method being similar to
that of A. yarrowii, described by Dr. Williston, and having an especial
interest, as it shows a transition stage between the wasps that
provide the store of food all at once and those that feed their young
all through the larval period. Urnaria rarely flies with her prey;
but this wasp, although her caterpillars, are not very much smaller,
and she herself is no larger, carries her booty lightly on the wing,
alighting only occasionally to run a few steps. She has to do more work
than urnaria, taking five or six caterpillars instead of two, and this
method of progression has the advantage of rapidity.
The first wasp that we saw was just alighting with a medium–sized
green caterpillar near a partly closed nest. When disturbed she flew
away, but soon returned, dropped her prey half an inch from the nest,
proceeded to clear the opening, ran inside to see that all was right,
and then backed in with the caterpillar. Emerging after a few minutes,
she placed a small pebble in the doorway, which was thus partly closed,
and flew away. She brought three more caterpillars at intervals of
thirty minutes, and then, after wedging a pebble into the neck of
the opening, she began to fill it in solidly, scratching in dirt and
packing in lumps of earth which were brought in her mandibles. We
did not allow her to complete this operation, as it would have made
excavation more difficult, but caught her and dug out the nest. The
tunnel ran down obliquely for five inches, being two inches below the
surface at the pocket. In it we found a wasp larva, which was at least
three days old, and four caterpillars. There were no signs of the
banqueting which must have already taken place. We carried this larva
home with us, and it ate the caterpillars up clean, finishing with a
fifth which we supplied from another nest, and going into its cocoon
on September sixteenth. The caterpillars all wriggled about on the
slightest stimulation, and remained in this lively state until they
were eaten. They belonged to four different species.
In a second nest to which food was being carried, we found four
caterpillars and a larva about three days old, all the conditions being
like those in the other example. Evidently the larva had been fed from
day to day, since four or five days must have elapsed since the making
of the nest.
Westwood states that Ammophila, when she has captured her prey, walks
backward, dragging it after her;[1] but in all the cases that came
under our notice she went forward, the caterpillar being grasped near
the anterior end, in her mandibles, and either lifted above the ground
or allowed to drag a little if long and heavy. It is usually held
venter up, but in one case, in which the wasp, while carrying it to her
nest, frequently laid it down and picked it up again, it was held with
the venter down or up indifferently.
The all–important lesson that Fabre draws from his study of the
Ammophiles is that they are inspired by automatically perfect
instincts, which can never have varied to any appreciable extent from
the beginning of time. He argues that deviation from the regular rule
would mean extinction. For example, if the wasp should sting ever so
little to one side of the median line the prey would be imperfectly
paralyzed and the egg would consequently be destroyed; or a sting in
the wrong place might cause the death of the caterpillar and thus the
death of the wasp larva, which, he thinks, can be nourished only by
perfectly fresh food.
The conclusions that we draw from the study of this genus differ
from these in the most striking manner. The one preëminent,
unmistakable, and ever present fact is variability. Variability in
every particular,—in the shape of the nest and the manner of digging
it, in the condition of the nest (whether closed or open) when left
temporarily, in the method of stinging the prey, in the degree of
malaxation, in the manner of carrying the victim, in the way of closing
the nest, and last, and most important of all, in the condition
produced in the victims of the stinging, some of them dying and
becoming “veritable cadavers,” to use an expressive term of Fabre’s,
long before the larva is ready to begin on them, while others live long
past the time at which they would have been attacked and destroyed if
we had not interfered with the natural course of events. And all this
variability we get from a study of nine wasps and fifteen caterpillars!
In his chapter on “Méthode des Ammophiles” Fabre says that each species
has its own tactics, allowing no novitiate. “Not one could have left
descendants if it were not the handy workman of to–day. Any little
slip is impracticable when the future of the race depends upon it.” And
yet we find that the prey may be stung so slightly that it can rear
and wriggle violently or so severely that it dies almost at once, and
in neither case is a break made in the generations of the Ammophiles,
since in the former the egg or larva is so firmly fastened as to keep
its hold, while in the latter the dead and decomposing caterpillar is
eaten without dissatisfaction or injury.
Nor do we, in gathering evidence for the evolution of the instincts of
these wasps, need to rely entirely upon our own observations. Fabre
himself gives many facts which point in the same direction, but he
draws a line between those actions which are the result of mechanical
and unvarying instinct and those which come within the sphere of
reason, and in relation to which the insect must consider, compare,
and judge. Yet this line, even in the light of his own work, is so
extremely variable, needing readjustment with every new species and
often among the individuals of the same species, that it loses for
others the meaning which it has for its author. He himself speaks of
certain individuals of the genus Sphex which refuse to be duped when
he withdraws their prey to a distance. These, he says, are the élite,
the strong–headed ones, which are able to recognize the malice of the
action and govern themselves accordingly, but these revolutionists, apt
at progress, he goes on to say, are few in numbers. The others, the
conservators of old usages and customs, are the majority, the crowd.
Yes, but is it not always the strong–minded few that direct the destiny
of a race?
Chapter III
THE GREAT GOLDEN DIGGER
THIS wasp (Sphex ichneumonea Linn.) is one of our most beautiful
species, its great size and its brilliant color, as it flies among the
flowers, serving to make it well known to all observers of nature.
During the later part of July, all through August, and even in the
early days of September it is commonly found at work making or storing
its burrow. It is rare in our garden, however, and we thought ourselves
fortunate in being able to keep track of one individual from the
making to the closing of the nest. Although large and powerful it is
gracefully formed. In color it is brown, varied with bright yellow.
On the morning of the third of August, at a little after ten o’clock,
we saw one of these hunters start to dig a nest on the side of a stony
hill. After making some progress in the work she flew off and selected
a second place, where she dug so persistently that we felt confident
that this was to be her final resting–place; but when the hole was two
and one half inches deep, it too was deserted. Again our wasp chose
a spot and began to burrow. She worked very rapidly, and at twenty
minutes before twelve the hole was three inches deep. At high noon she
flew away, and was gone forty minutes. The day was excessively hot,
about 98° Fahr., and we ourselves were only deterred from taking a
noonday rest by our fixed determination not to leave the place until we
had seen all that there was to be seen in the manœuvres of ichneumonea.
On returning she appeared very much excited, fairly quivering with
vitality as she resumed her work. She came up backward, carrying the
earth with her mouth and anterior legs, and went back from the opening
some little distance, when it was dropped, and she at once went in
again. While in the burrow we could hear her humming, just as the
Pelopæi do when, head downward in the wet mud, they gather their loads
for nest–building. In five or six trips a little mass of earth would
accumulate, and then she would lie quite flat on the heap and kick the
particles away in all directions. As the work progressed the earth was
carried further and further away before it was placed on the ground,
and as she backed in different directions the material brought out was
well spread about from the down–hill side of the nest. Sometimes she
would spend several moments in smoothing the débris all around, so
that the opening presented much the appearance of an immense ant–hill,
only the particles were much larger. During the first hour that we
watched her she frequently turned directly toward us, and, sometimes
remaining on the ground and sometimes rising on her wings to a level
with our faces, appeared to be eyeing us intently for four or five
seconds. Her attitude was comical, and she seemed to be saying, “Well,
what are you hanging around here for?”
[Illustration: THOROUGH LOCALITY STUDY BY SPHEX]
As the afternoon wore on she worked more calmly and her fidgety and
excited manner disappeared, the excavation progressing steadily until
half–past three. At that time she came out and walked slowly about in
front of her nest and all around it. Then she rose and circled just
above it, gradually widening her flight, now going further afield and
now flying in and out among the plants and bushes in the immediate
vicinity. The detailed survey of every little object near her nest was
remarkable; and not until her tour of observation had carried her five
times entirely around the spot did she appear satisfied and fly away.
All her actions showed that she was studying the locality and getting
her bearings before taking her departure. A fact that impressed us very
much was that with the two nests that she had begun and then deserted
she had taken no such precaution, but simply came up and flew off.
Had she made up her mind, if we may be allowed to use the term, that
the localities were in some way unsuitable and that hence she had no
occasion to return to them? Had she decided, in the last instance, that
she would return and so must get her bearings? We wondered how far the
different acts were instinctive, or were, as Huber has it, an evidence
of a “little dose of judgment.” Bates, in speaking of Monedula signata,
says that he often noticed it taking a few turns about the locality
of its nest, and that he was convinced that it was doing so for the
purpose of getting its bearings. Belt, having described how he fed a
specimen of Polistes carnifex with a caterpillar, which the wasp cut
into two parts, goes on to say: “Being at the time amidst a thick mass
of fine–leaved climbing plant, it proceeded, before flying away, to
take note of the place where it was leaving the other half. To do this,
it hovered in front of it for a few seconds, then took small circles
in front of it, then larger ones around the whole plant. I thought it
had gone, but it returned again, and had another look at the opening
in the dense foliage down which the other half of the caterpillar
lay.”[2] He then remarks that when the wasp came back for the remaining
half it flew straight to its nest without taking any further note of
the locality. Both of these writers believe that many of the actions
of insects that are ascribed to instinct are really evidence of the
possession of a certain amount of intelligence.
[Illustration: HASTY LOCALITY STUDY BY SPHEX]
To return to our Sphex. When she flew away we naturally supposed that
she had gone in search of her prey, and we were on the _qui vive_ to
observe every step in her actions when she came home. Alas! when she
came back half an hour later, she was empty–handed. She dug for four
minutes, then flew off and was gone two minutes, then returned and
worked for thirty–five minutes. Another two minutes’ excursion, and
then she settled down to work in good earnest and brought up load
after load of earth until the shadows grew long. We noticed that on
these later trips she flew directly away, depending upon her first
careful study of the surroundings to find her way back. At fifteen
minutes after five the patient worker came to the surface, and made a
second study, this time not so detailed, of the environment. She flew
this way and that, in and out among the plants, high and low, far and
near, and at last, satisfied, rose in circles, higher and higher, and
disappeared from view. We waited for her return with all the patience
at our command, from fifteen minutes after five until fifteen minutes
before seven. We felt sure that when she came back she would bring her
victim with her, and when we saw her approaching we threw ourselves
prone on the ground, eagerly expecting to see the end of the drama; but
her search had been unsuccessful,—she carried nothing. In the realms
of wasp–life, disappointments are not uncommon, and this time she had
us to share her chagrin, for we felt as tired and discouraged as she
perhaps did herself. When we saw her entering without any provision
for her future offspring, we were at a loss what to do next; and it
may be that this state of mind was shared by her also, for she at once
began to fill in the entrance to her nest. We now thought it time to
act, and decided to capture her, to keep her over night in one of our
wasp–cages, and to try to induce her to return to her duty on the
following day. We therefore secured her in a large bottle, carried her
to the cottage, and having made every possible arrangement for her
comfort, left her for the night.
[Illustration: SPHEX DRAGGING GRASSHOPPER TO HER NEST]
On the next morning, at half after eight o’clock, we took Lady Sphex
down to her home, and placed the mouth of the bottle so that when she
came out she had to enter the nest. This she did, remaining below,
however, only a moment. When she came up to the surface she stood still
and looked about for a few seconds, and then flew away. It surprised
us that having been absent from the place for so many hours, she made
no study of the locality as she had done before. We thought it a very
unpromising sign, and had great fears that she was deserting the place
and that we should see her no more. One would need to watch a wasp
through the long hours of a broiling hot day to appreciate the joy
that we felt when at nine o’clock we saw her coming back. She had no
difficulty in finding her nest, nor did she feel any hesitation as to
what ought to be done next, but fell to work at once at carrying out
more dirt. The weather, although still hot, had become cloudy and so
threatening that we expected a down–pour of rain every moment, but
this seemed to make no difference to her. Load after load was brought
up, until, at the end of an hour, everything seemed completed to her
satisfaction. She came to the entrance and flew about, now this way,
and now that, repeating the locality study in the most thorough manner,
and then went away. At the expiration of an hour we saw her approaching
with a large light green meadow–grasshopper, which was held in the
mouth and supported by the fore legs, which were folded under. On
arriving, the prey was placed, head first, near the entrance, while the
wasp went in, probably to reassure herself that all was right. Soon
she appeared at the door of the nest and remained motionless for some
moments, gazing intently at her treasure. Then seizing it (we thought
by an antenna) she dragged it head first into the tunnel.
The laying of the egg did not detain her long. She was up in a moment
and began at once to throw earth into the nest. After a little she went
in herself, and we could plainly hear her humming as she pushed the
loose material down with her head. When she resumed the work outside we
interrupted her to catch a little fly that we had already driven off
several times just as it was about to enter the nest. The Sphex was
disturbed and flew away, and this gave us an opportunity to open the
burrow. The grasshopper was placed on its back, with its head next to
the blind end of the pocket and the legs protruding up into the tunnel.
We found that the egg of the wasp, which was seven millimeters long,
and rather slender, was placed on the under face of the thorax at a
right angle to its length, and parallel with the femur of the second
leg. This leg had apparently been stung so that it had swollen and
folded over the free end of the egg, which was thus firmly held in
place at both extremities.[3] Upon examination we found that the
abdomen of the grasshopper was beating regularly and automatically,
but the closest observation failed to discover any other movements,
nor would any part respond when stimulated. At three o’clock in the
afternoon we found the abdomen still pulsating, and, in addition, that
both antennæ moved several times when we lifted off the cover of the
jar that contained the insect. On the next morning the grasshopper was
very lively, the antennæ and labial palpi moving without stimulation.
It had passed fæces, and was able to lift its abdomen, which was
curved over toward the head, as it lay on its back, frequently and
with considerable violence. On the next afternoon there was no change
in the movements, but the egg was dead. On the seventh the grasshopper
responded to stimulation by a slight movement of the palpi and the
end of the abdomen. The pulsation of the abdomen continued until the
afternoon of the eighth, when it ceased, no effort of ours succeeding
in starting it again. The movements of the antennæ and palpi grew
weaker and weaker on the ninth, and on the morning of the tenth the
insect was dead, a period of five and a half days having elapsed since
it was brought into the nest.
We had not supposed that the digging up of her nest would much disturb
our Sphex, since her connection with it was so nearly at an end; but
in this we were mistaken. When we returned to the garden about half an
hour after we had done the deed, we heard her loud and anxious humming
from a distance. She was searching far and near for her treasure
house, returning every few minutes to the right spot, although the
upturned earth had entirely changed its appearance. She seemed unable
to believe her eyes, and her persistent refusal to accept the fact
that her nest had been destroyed was pathetic. She lingered about the
garden all through the day, and made so many visits to us, getting
under our umbrellas and thrusting her tremendous personality into our
very faces, that we wondered if she were trying to question us as to
the whereabouts of her property. Later we learned that we had wronged
her more deeply than we knew. Had we not interfered she would have
excavated several cells to the side of the main tunnel, storing a
grasshopper in each. Who knows but perhaps our Golden Digger, standing
among the ruins of her home, or peering under our umbrella, said to
herself: “Men are poor things: I don’t know why the world thinks so
much of them.”
[Illustration: NEST OF SPHEX]
Dr. Packard describes Sphex ichneumonea as nesting in gravelly walks,
where it digs to a depth of from four to six inches, using its jaws
and fore legs to do the excavating. While the wasps that he observed
completed the hole in half an hour, ours was actually at work a little
over four hours. Her nest, as is shown in the drawing, measured
seven and one half inches to the beginning of the pocket, which was
three quarters of an inch wide by one and one half inches long. The
yellow–winged Sphex, a native of France, was found by Fabre to take
several hours to make her nest, working in hard ground; while another
species, also studied by this observer, dug in soft earth, either in
the ground or in the accumulations on the roofs of buildings, and
completed her work in fifteen minutes at the most. These variations in
the habits of closely related species should be carefully studied in
any attempt toward an explanation of their instincts.
Fabre’s account of the genus Sphex, as it appears in France, is
most interesting. He says that the yellow–winged species, living in
colonies, first digs her nest and then secures her cricket, which is
brought, on the wing, to the neighborhood of the burrow, the last part
of the journey being accomplished on foot. The cricket is dragged by
one of the antennæ, and is not left until the nest is reached. It is
then placed so that the antennæ reach precisely to the opening, and
there it is left while the wasp descends hurriedly into the depths of
the burrow. In a few seconds she reappears, showing her head outside,
seizes the antennæ of the cricket, and drags it below. These manœuvres
are repeated with a striking degree of invariability.
The other Sphex first secures her prey, which is too large and heavy
to be carried far, and then digs her nest in the neighborhood of the
capture. This being done, she returns to her victim, and straddling it
drags it by one or both of the antennæ. Sometimes the whole journey is
accomplished at once, but oftener the wasp suddenly drops her burden
and runs rapidly to her nest. Perhaps it seems to her that the entrance
is not large enough to accommodate a creature of such size; perhaps she
imagines some imperfections of detail which would impede the process
of storing it up. The work is retouched, the doorway enlarged, the
threshold smoothed. Then she returns to her booty and again starts
with it. After a few steps the Sphex seems to be seized with another
idea. She has visited the doorway, but has not seen the interior. Who
knows whether all is well within? She drops her prey and again runs
off. The visit to the interior is made, more touches are given, and
once more she returns. Will the journey be accomplished this time?
Impossible to say. Some wasps, more given to worry than others or more
forgetful of the small details of architecture, to repair their neglect
or to clear up their suspicions, abandon their booty five or six times
in succession to retouch the nest or simply to visit the interior. The
prey, once brought to the nest, is carried in without the preliminaries
that are common to the other species.
Chapter IV
SEVERAL LITTLE WASPS
In a search for the nest of one of our garden wasps we found, in the
woods beyond the fence, an old, weather–beaten stump which was riddled
with holes both large and small. The large ones were evidently the
passage–ways of ants, and were in constant use. The small ones seemed
to be uninhabited; but thinking they might contain the nests we were
in search of, and hoping that if we watched long enough we might see
our wasps flitting in and out, we settled ourselves close by. We
were resolved to stay as long as was necessary, and we blessed the
fate that made it our duty to sit on the grass under the shade of a
wide–spreading oak rather than in the distressing glare and heat of the
garden; for this was on the tenth of July, and the weather was what the
farmers call “seasonable.”
Twenty, thirty, forty minutes passed. Our eyes ached with persistent
gazing, and we had nearly made up our minds that the likely–looking
little holes were untenanted, when lo! a tiny wasp, carrying something
which we could not see distinctly, darted into one of them. It was
gone so quickly that we could not be sure that it was the species we
were looking for, and when it reappeared, after two or three minutes,
we saw that it was not. This point being determined, we watched the
hole with redoubled interest.
It was wearisome work, for the wasp stayed away a long time, and we
dared not let our gaze wander lest she should slip in without our
knowledge. At the end of thirty–five minutes she returned, but again
we failed to see what she carried. She flew with great rapidity, and
we scarcely caught sight of her before she vanished into her nest.
We could not but wonder at the ease and certainty with which she
recognized her own doorway among the hundreds of holes on the side of
the stump. This power of localization, while it is one of the most
common among wasps, is surely also one of the most remarkable.
Our little Rhopalum pedicellatum, for that proved to be her name, made
six more journeys within the next two hours. At the end of this time
we opened the tunnel, and, after a great deal of sawing and cutting,
succeeded in finding the nest five inches from the surface. It was
nothing but a slight enlargement of the gallery, in the soft decaying
wood. In it we found thirty–three gray gnats, all of them, except two,
being dead. On one of the dead ones was the egg, which had probably
been laid within a few hours.
The egg hatched two days later, on July twelfth, but on the fifteenth
the larva died. By this time many of the gnats looked very dry,
although we had tried to arrange for both moisture and ventilation by
packing the bottom of the tube with pith and covering the top with
muslin.
Further watching gave us one more wasp of this species, in the same
stump. This time the nest was only two inches from the surface. It
contained four dead gnats and two live ones, but no egg, showing that
the egg is not always laid on the first ones stored.
Much later in the season, toward the end of August, we found another
species of Rhopalum which proved to be new, and for which Mr. Ashmead
has proposed the name rubrocinctum, since it wears a red girdle around
the front end of the abdomen, being otherwise dressed in black like
pedicillatum. It makes its home in the stalks of raspberry bushes.
We opened a stem which contained thirteen compartments, separated by
partitions of pith. These were filled with black, gray, and green
gnats, which were packed in so closely that they were doubled over and
pressed out of shape. Each cell contained from twenty–five to thirty
gnats. In some of them were cocoons, in others larvæ, and in one was
an egg. The gnats were very carefully examined, and all of them, from
the cells that had been filled last as well as from those provisioned
earlier, were dead.
Other species of Rhopalum are said to prey upon spiders and aphides.
In studying the species that come in our way we are continually
developing distinct likings for some kinds above others. The appearance
of one of these favorites is always hailed with delight, and when the
season’s work is over we remember them with lively pleasure.
[Illustration: OXYBELUS QUADRINOTATUS]
It is thus, dear little Oxybelus, that we dwell upon the thought of you
and your pretty ways. No other wasp rose so early in the morning, no
other was so quick and tidy about her work, so apt and business–like
without any fuss or flurry. No other was more rapid and vigorous in
pursuit of her prey, and we think with admiration and gratitude of
the number of flies that you must have destroyed in the course of the
summer.
O. quadrinotatus is only one–quarter of an inch long, and is dark gray
with four whitish spots on the abdomen. It was before nine o’clock
in the morning that, while out on an early inspection tour in the
garden, we saw one of these wasps descend upon a sandy spot, and after
a moment’s rapid scratching with her first legs enter the hole that
she had opened. Under her body she was carrying a fly which looked
like the common domestic species. It was upside down, its head being
tightly clasped with the third pair of legs, and all of its abdomen
projected beyond the abdomen of the wasp. Ashmead quotes from Fabre the
remarkable statement that Oxybelus carries her flies home impaled on
her sting, an idea that probably arose from the fact that nearly the
whole body of the fly is visible.
Our new–found wasp stayed only a moment in her nest, although, as we
afterward found, it was long enough for her to lay her egg on the fly.
When she came out she quickly smoothed the sand over the spot with her
head and legs so that there was nothing to mark the nest, and flew
away. In three minutes she returned with another fly. She alighted two
or three inches away, and scratched for an instant, but quickly saw her
mistake, and found the right spot.
Again and again the pretty little worker went and came, while we sat
watching close by, admiring her deft handiwork in opening and closing
the nest and wondering at the ease with which she found it at each
return. There was nothing tiresome or dilatory about this species, and
within twenty minutes we had seen six flies stored up. The nest was
closed and the place smoothed over every time before she went away, but
when she entered she left the door open behind her. We once tried to
make her drop the fly, but when disturbed she flew up and alighted on a
plant near by, keeping her hold on it. The whole performance was brisk
and business–like, but without the feverish hurry of Ammophila and
Pompilus.
After the sixth fly was taken in we were afraid to let her go again,
thinking that the nest must now be completely provisioned, and that she
would not return. She was such a charming little wasp, scarcely bigger
than a fly herself and yet so useful in her industry, that we hated to
disturb her; but as we were obliged to have her for identification we
first caught her, and then opened the nest. It contained only the flies
that we had seen taken in, the egg being attached to the one lowest
down, on the left side, between the head and the thorax. It was long
and cylindrical. The flies were dead, but showed no marks of violence.
We learned later that it takes Oxybelus two hours to make her nest so
that this one must have been prepared the day before.
The egg, which was laid just before nine o’clock on the morning of
August seventh, hatched at a little after nine on the morning of August
eighth. The larva began to eat at once, and devoured all the inside
of the thorax and abdomen of the fly to which it was attached, in the
first twenty–four hours. On August twelfth it had reached the sixth
fly, and we supplied it with three more. On August fourteenth these
were gone, and we again replenished its larder, this time with two
flies. The larva had partly eaten these when something went wrong. Its
appetite failed, and on August sixteenth it died.
On further acquaintance this wasp lost none of her charm,—indeed, she
gained in interest from the almost human curiosity that she showed
about the affairs of other people. Where several were living close
together one of them would sometimes stop digging her own nest to perch
on a weed and watch the labor of another, and we once saw an especially
inquisitive character burrow through the closed door and enter the home
of her next–door neighbor.
[Illustration: NEST OF OXYBELUS]
We find but meagre notes on the genus Oxybelus. Ashmead says that
no observations have been made on the American species, but that in
Europe they are found to burrow in sand and to provision their nests
with dipterous insects. He says also that according to Verhoeff the
species in this genus do not paralyze their prey by stinging, as they
are unable to do so on account of the rigidity of the abdomen, but
that instead they crush the thorax with the mandibles just beneath
the wings, the centre of the nervous ganglia. He found in one nest
a dozen flies, and all had the thorax crushed and were dead. In the
case of our wasp we do not know how the flies were killed, but there
was no crushing of the thorax. The larva devoured, in all, ten flies.
At the time of its death it had probably finished the larval stage
of its existence, since nine days had elapsed since the hatching
of the egg. It may be that this period just before pupation is a
critical point in the life history of a wasp, for we lost several of
our nurslings at this time, and Fabre has noted that when, on account
of the presence of parasites, the larva of Bembex rostrata had lacked
something of its usual amount of nourishment, it perished miserably at
the end of its larval stage, not having strength enough to spin its
cocoon. No waspling in our charge ever died from lack of nourishment—on
that score our consciences are clear; but it was difficult to make
their conditions quite normal, and for this reason we may have been,
indirectly, the cause of their death.
The way in which our Oxybelus carries its prey is peculiar to itself.
Bembex and Philanthus also hold their prey under the body, but use the
second pair of legs, so that it does not project behind except at the
moment of entrance into the nest. Quadrinotatus, as we could distinctly
see, since she passed close to us several times in quick succession,
clasps the head of her victim in the third pair of legs, and flying
thus, with its whole body sticking out behind her, she certainly
presents a very remarkable appearance.
[Illustration: APORUS FASCIATUS]
Aporus fasciatus is a dark gray species, and is less than half an inch
in length. We were working one hot day in the melon field, when we
saw one of these little wasps going backward and dragging a female of
Mævia vittata which was much larger than she was herself. She twice
left it on the ground while she circled about for a moment, but soon
carried it up on to one of the large melon leaves, and left it there
while she made a long and careful study of the locality, skimming close
to the ground in and out among the vines; at length she went under a
leaf that lay close to the ground and began to dig. After her head
was well down in the ground we broke off the leaf that we might see
her method of work. She went on for ten minutes without noticing the
change, and then, without any circling, flew off to visit her spider.
When she tried to return to her hole it was evident that some landmark
was missing. Again and again she zigzagged from the spider to the
nesting–place, going by a regular path among the vines from leaf to
leaf and from blossom to blossom, but when she reached the spot she did
not recognize it. At last we laid the leaf back in its place over the
opening, when she at once went in and resumed her work, keeping at it
steadily for ten minutes longer. At this point she suddenly reversed
her operations and began to fill the hole that she had made, kicking
in the earth until the entrance was hidden. She then glanced at the
spider, selected a new place, and began to dig again. Surprisingly
large pellets of earth were carried out, backward, and loose dirt was
kicked under the body by the first legs. At the end of two or three
minutes she paused and remained perfectly still for a time, considering
the situation. Her conclusion was adverse to the locality, for she
soon filled in the hole, looked once more at the spider, and started a
third nest in a new place. This in turn was soon abandoned, as was also
a fourth. The fifth beginning was made under a leaf that lay close to
the ground, so that we could not see her at all. Fasciatus! had we had
the naming of her she should have gone down the ages as exasperans! We
had now watched her for an hour in the intense heat; the bell for the
noonday meal had sounded, hunger and thirst had descended upon us, and
most devoutly did we hope that she was suited at last, but no—after
twenty minutes’ work this place also was abandoned, and a sixth nest
started. This, however, was the final choice, and after forty–five
minutes spent in digging, it was completed. As the spider was brought
toward the nest it was left again and again while the nervous little
wasp flew to the hole, went in, examined, and came out again. At last
she backed in, caught the spider by the abdomen, and dragged it down.
It was too big—the head stuck in the hole; but she pulled from below
while we pushed gently from above, and it slowly disappeared. When she
came out we opened the nest and took the spider. The egg was fastened
to the middle of the left side of the abdomen. This one, as was also
the case with a second and third afterward taken from fasciatus, was
much less affected by the poison than is usual among the victims
of solitary wasps, moving from the time it was taken, without any
stimulation, and improving rapidly from day to day. Our second spider
appeared to be blind, and died upon the sixteenth day, while the third
had entirely recovered by the seventeenth day after it was stung, and
was released. Fasciatus, then, probably depends upon packing her victim
in tightly to keep it quiet.
It was three days and a half before the egg that we had taken hatched.
The larva developed rapidly, retaining its hold at the spot to which
the mother had fastened it. The spider remained alive for six days,
and the larva continued to grow for two days longer, when it died
also, being at the time about two thirds grown. We had great trouble in
protecting our growing larvæ from the inroads of fungi, and this was
one of the many that perished from that cause.
The next example of fasciatus that came under our notice was a
remarkable contrast to the one that we have just described, being as
slow and dignified as the other was nervous and hurried. She chose
a place and kept to it, her steady labor being interrupted only by
occasional visits to the spider; but it took her fifty minutes to
complete the nest. When finished it was a small gallery running down
obliquely for an inch and a half into the ground.
The only habit that this species can claim as peculiar to itself is the
strange and useless one of filling up the partly made nests that it is
about to abandon. We have never seen the sense of order carried to so
high a point in any other wasp.
[Illustration: WASP HOMES IN THE LOG CABIN]
On a hillside near our cottage stands a log cabin, deserted and
untenanted save for small creatures of the wild, which, though a
favorite spot with wood–boring wasps, is an unprofitable place for
study because of the difficulty of cutting out their nests without
destroying property. One day in early July, however, when we were
in the full fervor of hunting and longed to utilize every moment,
the wasps in our garden seemed to have resolved that enjoyment
and enjoyment only was their destined end and way, and became so
exasperatingly idle that in disgust we turned to the cabin. For half
an hour we saw nothing more exciting than a Trypoxylon immuring her
victims and a Pompilus hunting spiders under the eaves, but at the end
of that time Passolocus annulatus, a tiny wasp new to us, came flying
quietly along and entered one of the holes with which the ends of the
logs were riddled. She was carrying an aphis in her mandibles, and when
this was duly stored she reappeared and flew away. She had probably
just renewed her work after a spell of rest, since from this time on
for nearly an hour she came back regularly every four or five minutes.
She nearly always alighted on a blade of grass before going into the
nest, but did not appear to be malaxing her prey. Presently another
stage in the game was reached. She no longer brought aphides, but
little pellets of mud with which she plastered up the opening. After
she had finished this task and departed, we carefully chiseled into the
log and laid bare the nest. The tunnel ran in for about three inches,
and ended in three pockets which were well stocked with dead aphides,
there being fifty–seven in all. The innermost cell contained a larva,
and in the others were eggs, one of which hatched on the next day and
one on the day following. This second one was probably laid just before
the nest was sealed, giving forty hours for the egg stage; and it
proved to be the healthiest of the three. The others perished in early
infancy; but this one passed twelve days in eating, not only its own
share of provisions, but those destined for the other members of the
family as well, and then spun its cocoon.
We afterwards saw many of these wasps working in the logs of the cabin,
and noticed that they seemed to have seasons of leisure alternating
with spells of active work, as though when one cell had been filled up
and the egg laid they felt at liberty to amuse themselves for a time
before beginning on another. When an entirely new residence was to be
chosen they went house–hunting among the old holes in the logs; and
whether they had a high standard of sanitary conditions, or whether
they objected to making extensive repairs, a great many places were
examined and rejected before they settled down. The choice once made,
many loads of pith were carried out before the little householder was
satisfied. After the new abode was put to rights, the wasp would pass
a whole day in rest, spending much of the time in looking out of her
doorway and perhaps in observing the doings of her neighbors, but when
she began to work she was very industrious, and allowed nothing to
interfere with her labors, paying no more attention to us, no matter
how closely our curiosity led us to interrogate her, than if we had
been trees blown about by the wind.
[Illustration: NEST OF PERENNIS]
Some of the wasps dig deep into the stems of bushes to form galleries
for their nests, but we found one wise genus that went in only far
enough to make one or two cells, thus saving the trouble of carrying
her cuttings thirty or forty centimeters in direct opposition to the
force of gravity. This was Odynerus, whose nests we found in July, in
blackberry and raspberry stems. Our first species was perennis, whose
nests bear her mark in the shape of a pellet of earth placed above
each mud partition. One of her cells contained a wasp larva and about
sixteen caterpillars, nearly one third of which were dead, while the
rest were more or less lively. They seemed to have been stung near
the anterior part, as the last three or four segments were jerked up
violently when touched. The larva went on eating, and the caterpillars
went on dying from hour to hour. At the end of the eighth day, the baby
wasp finished its meal, having eaten all that had been provided for
it, as well as two dead caterpillars from another nest.
Much interest attaches to the way in which Odynerus lays her egg, since
instead of following the common fashion of fastening it to the prey she
suspends it by a tiny filament of web from the wall or ceiling of her
cell. Thus in O. reniformis, nesting in the ground, it is hung from
the ceiling, a mass of very imperfectly paralyzed caterpillars being
collected below, and when the larva comes out the thread lengthens
until the tiny jaws reach the food supply. Startle it ever so slightly
and the waspling retreats by way of its web, descending again only when
everything is quiet. For twenty–four hours it retains this path to
safety, and then, growing bold, it drops down and feeds at its ease.
We had opened hundreds of plant stems in quest of these suspended eggs
without being so fortunate as to find one, and were therefore much
pleased when our kind friend, Dr. Sigmund Graenicher, whose interest
in bees keeps him in touch with out–of–door happenings, and who has
given us much valuable help, brought us two stalks, one of which had
in it a nest of O. conformis, while the other contained two freshly
provisioned cells of O. anormis. In all three the egg had been hung
from the side of the cell about one third of the way down, and in
the nest of conformis, from which all but one of the caterpillars had
fallen, it hung loose against the wall. In the other nests the lower
part was packed tightly with sixteen small larvæ, upon which lay the
egg, supported in a horizontal position, although attached to the side
wall exactly as in conformis, and above were eight more caterpillars,
the whole forming a compact mass shut in by the usual partition of mud.
So closely were they crammed in that after counting them we were unable
to get them all back again, and although motionless in their narrow
quarters they became quite active when relieved from pressure. This
is an entirely different arrangement from that of O. reniformis, and
since the larva is in contact with the caterpillars from the moment of
hatching the manner of the egg–laying has no significance in relation
to the safety of the young.
[Illustration: NEST OF ANORMIS]
Conformis hatched on the morning after we received it, sloughing off
the skin of the egg, but remaining attached to it, and thus doubling
the length of the thread by which it hung. The caterpillar was slightly
separated from it, and it seemed to have no notion of feeling about
for its food, eating nothing for twenty–four hours, but growing and
developing nevertheless. We now piled up some caterpillars in contact
with it, and it began to eat, but after its own caterpillar and as many
as we dared take from anormis were gone it stubbornly refused to take
soft, tender little spiders, or caterpillars out of our garden; and it
perished, a victim to prejudice.
The two eggs of anormis were probably laid within a few hours of each
other, since they had both hatched on the morning of the third day,
and had broken from their attachment, beginning to eat at once. They
cocooned on the fifth day after hatching.
We had long wished to find a nest of O. capra, and early in September
fortune favored us. A neighbor of ours keeps a large tin horn hanging
under the porch. One day when she wished to use it, no amount of
blowing would bring forth a sound; and when she unscrewed the
mouthpiece to investigate the matter, out tumbled several small green
caterpillars and a quantity of dry mud. When we heard of this incident
we begged that if it should be repeated the nest and its contents
might be saved for us; and on the second of September we received the
mouthpiece of the horn with a message to the effect that a wasp had
been working at it for some days. Examination showed that there were
three cells, each containing a larva and a supply of caterpillars,
of which there were ten in the cell most lately formed, and only one
left uneaten in the oldest. The caterpillars, all of them being alive,
together with the wasp larvæ, were transferred to a place in which they
could be conveniently watched. None of the caterpillars died until
they were attacked. The larvæ ate all the food that was provided, the
oldest one cocooning on the fourth, and the second one on the seventh
of September. Of the third, we have no record, excepting that the
caterpillars had all been eaten on September eighth.
We happened to be passing through our neighbor’s grounds at nine
o’clock on the morning of September fifth, and calling to ask whether
there had been any more visits from the wasp, we learned that capra had
been seen making a mud partition in the horn on the day before. While
we were speaking she arrived and entered the mouthpiece, where she
remained for about ten minutes. When she departed we found that she had
laid her egg, which we carried away with us, wishing to determine the
length of the egg stage. This proved to be longer than that of any wasp
that we had heretofore known, for not until the morning of September
ninth did the larva make its appearance, the egg skin bursting and
leaving its tenant free to crawl away. In other genera the egg changes
into a larva imperceptibly, there being no sloughing off of the skin.
Capra, then, first finds a suitable crevice, and builds a partition
across the inner end, the earth being scratched up from some dry, bare
spot, and moistened in her mouth. Before gathering the ten or twelve
small caterpillars that are to provision the cell, she lays her egg;
and although we could not be sure, we thought that in this case as in
the others it was suspended.
Unless the cell is tightly packed at the beginning, capra certainly
needs the filament, for her caterpillars were so far from being
reduced to a state of decent immobility that we had to press wads of
cotton into the tubes in which they were kept to prevent them from
wriggling out of the way of the larva. None of our larvæ, not even the
one–day–old ones, were injured by their activity; but had the egg been
left to its fate among them it might have perished.
Later in September we found O. vagus bringing pellets from a
sharp–edged hole in the ground. Her method was to carry each load on
the wing to a distance of ten or twelve inches, where it was dropped
without the lively fling with which Ammophila discards her lump of
dirt. The red end of a match stuck into the ground two inches away
proved very disquieting to the dainty little wasp. These colored
matches were a great convenience in marking nests, and as we were
using them constantly, we did not guess, for a time, what the trouble
was. For half an hour she went and came, circling about, alighting
upon plants, and seeming entirely absorbed in examining them with
the minutest care, even alighting upon our hands with most engaging
friendliness, but pretending all the time that the nest was naught to
her. When the offending object was removed she hurried in at once and
resumed her work. The storing was not begun until the next morning,
when she took in six caterpillars of very different sizes, at intervals
of from ten to twenty minutes, and then filled the hole. We hoped to
find the little chamber arranged as in reniformis, but had not skill
enough to excavate in such a way as to show the internal plan. It is
remarkable that this genus, with only one set of tools for all its
species, has worked out such different styles of architecture, the
ground nests bearing no resemblance to those cut out of woody stalks;
and its flexibility is shown in the use of empty snail shells by a
foreign species, as well as by capra’s habit of partitioning off
convenient crevices found ready made.
The prettiest nests that we have seen in stems are those of Plenoculus
peckhamii, which separates its cells, not by solid partitions, but by
numerous granules of earth, which are used by the larvæ for forming
the case of the cocoon. One raspberry stalk that we opened had at the
bottom six of these mud cocoons, and above these three larvæ eating,
each in its own compartment, the provision in this case consisting
of immature bugs of the genus Pamera. Sometimes the stalk which is
being filled by Plenoculus attracts the fancy of a bee or of another
wasp, as is shown by the upper cells being filled by Osmia or Crabro,
or sometimes Plenoculus builds above the bee cells. When a number of
wasp eggs are placed in a plant stem, the last one laid is the first
to hatch. The different habits of the Hymenoptera in this respect are
very interesting. In the case of Ceratina dupla, the small carpenter
bee, the egg first laid hatches first, those above following in regular
order. The lower ones wait patiently in their cells until the one in
the top cell has matured, and then they all come out at once. When two
species occupy the same stalk, the lack of adjustment probably results
in the destruction of those lower down, excepting in the case of the
cuckoo flies, which have acquired the habit of gnawing their way out at
the side of the stem.
Chapter V
CRABRO
THE highest point of the island is crowned by a great group of linden
trees; and one day their perfume, carried by the wind far over field
and wood, was calling everything that had wings to gather the richest
of all the gifts that July can offer. We, too, were drawn to the spot,
and found the great blossoming domes thrilling and vibrating with life.
For miles around, the bees, wasps, and butterflies had gathered to the
feast; and we seemed to touch the high–tide of the year in the scent of
the flowers, the humming throng of happy creatures, and the vision of
it all against the summer sky.
Below, in a great root that had pushed above ground, five little
wasps, by name sexmaculatus, of the worthy but unimaginative genus
Crabro, resisting the intoxication of the linden flowers, were sawing
and cutting in the most humdrum and practical manner. One of them,
presumably the earliest riser, was well down in the root, and came
backing up once in a while, pushing a lot of wood dust out of the
hole. This was spread out by means of legs and mandibles, and was then
blown away by the fanning wings of the little worker, who circled about
just above the ground until the last grain had disappeared. Here was
another way of protecting the home. The fresh dust might attract the
attention of some cuckoo–like insect who would lay her egg within; and
therefore it was dispersed, just as Ammophila carried out her pellet
and flung it to a distance, and Sphex spread evenly over the ground the
mass of earth that she carried from her hole.
After this series of actions had been repeated several times the wasp
flew away to hunt. We afterward found that she had finished the third
in a set of cells leading from a main gallery. On her return we delayed
her to see what she was carrying. She showed no fear, but alighted
close by, and while she was trying to transfer to the third pair of
legs the fly that she was clasping with the second pair, it escaped and
flew gayly away. Flies are plenty, however, and she soon had another
which she was permitted to store; and from that time she worked busily
until we left her at noon. It took her from two to ten minutes to
catch her fly, and at each return two or three minutes were spent in
the nest. On opening her tunnel some days later, we found within not
only flies, but long–bodied gnats, and all of them seemed to have been
brought home uninjured. When the freshest cell was opened some flew
away, others were walking about, and all were lively. The wasp egg
was laid on the under side of the neck; and although we could not be
certain of the exact time of laying we thought it hatched at the end
of thirty–six hours. From ten to sixteen flies were provided for each
larva.
[Illustration: SEXMACULATUS IN THE LINDEN ROOTS]
A month later we found Crabro lentus nesting in the ground. Her
tunnel ran down obliquely for six and one half centimeters, and had
an enlargement at the end. Two bugs and a fly were in the nest, when
we opened it before the provision was completed. To find sexmaculatus
taking both flies and gnats was surprising, so rigid are the family
traditions of the wasps; still, she might feel that so long as she drew
the line at Diptera she was all right. But to believe that one wasp, a
Crabro, too, with all the marks of conservatism about her, would take
such diverse things as bugs and flies, is almost too much to believe.
It is true that Crabro wesmæli is said to use both flies and bugs;[4]
but some accident may have led to this supposition, and stronger
evidence is needed to prove that there is variability in so deeply
seated an instinct.
[Illustration: CRABRO AND HER WHITE MOTHS]
The Crabro wasps all have pleasant ideas as to where they want to
live, but interruptus excels in the choice of a dwelling place. We
lately found ten or twelve of them in Milwaukee, nesting in an old log
on the shore of Lake Michigan, and when they opened their doors in
the morning they had before them the splendor of the great bay; but
calm in the midst of the glory they never paused on the threshold, as
Cerceris would have done, to take a look at the world before going to
work. One morning the earliest riser in our little colony was beginning
the day at half past nine. Of good size for a Crabro, with a square
determined–looking head and very direct and business–like manners, she
proceeded to cut out a new chamber for provisioning. These chambers are
nothing more than enlargements of the long gallery, such as are made
in stems by related species. At ten o’clock she departed on a hunting
excursion among the bushes on the bank above us, and came back in eight
minutes, carrying, much to our surprise, a white–winged moth, which
was clasped under the body by the second and third pairs of legs, and
was passed back to the third pair as she alighted before entering. A
moth is an innovation, a delicacy new to the accepted idea of what a
Crabro larder, accustomed to Diptera, should contain. A moment later
she was off again, but this time did not succeed so quickly, coming
back twice empty–handed for brief visits, and bringing in a load at
the end of half an hour. It took six moths to provision the cell, and
as the number neared completion her interest and energy seemed to wax
greater, the hunting intervals shortening to five, and even to two
minutes. We found afterwards that some of the moths were alive and some
dead, and that she packed them lengthwise, one after another, into the
closely fitting chamber. At a little before eleven o’clock the cell
was filled, and the wasp retired from sight, closing the door behind
her. We thought that she was resting, but presently the protrusion of
wood dust showed that she was enlarging her house, and an hour later
she came out and began to hunt again. By this time half a dozen were
working. Before leaving for the first time in the morning each one made
a thorough study of the place, and on returning they entered their own
doors, which were standing open, without hesitation, the long white
wings of the moths trailing behind them. Four species were represented
in the nests that we opened.
[Illustration: CRABRO STIRPICOLA]
Many species of Crabro make their nests in the stems of plants, and
among these is stirpicola, which is seen in numbers, through the middle
of July, flying about in a leisurely way, though it is only toward the
end of the month, or in the early days of August, that they settle
down to the work of making their homes. On the afternoon of July
twenty–seventh, after some very lively work in the heat of the day, we
walked down to the berry garden at half past five o’clock, rather to
rest ourselves than with the thought of undertaking anything new; but
a wasp–hunter cannot afford to choose his own hours, and we thankfully
accepted the sending of fortune when we came upon a stirpicola busy at
work in digging out her nest. She had only begun to excavate, and had
reached a length just equal to that of her own body. Her manners were
an agreeable contrast to those of the wasps that we had been watching
through the day. The feverish excitement of their ways seemed quite in
keeping with the burning heat of noon, while Crabro’s slow and gentle
movements harmonized perfectly with the long shadows of evening. To
fully appreciate the difference between Pompilus or Ammophila and
Crabro it is necessary to see them at work. The one is the embodiment
of all that is restless, vying with the humming–birds in swiftness and
energy, while the other is calm, quiet, and stately in all that she
does.
[Illustration: BOTTLE ON STEM TO MEASURE WORK OF CRABRO]
Some ten feet away was a second stirpicola, and this one, to judge
from the depth to which she had penetrated, must have been at work
for about two hours. We watched them both, and saw them bring up load
after load of pith. They bit out the pellets with their mandibles, and
passed them back between the legs and under the body until a quantity
had accumulated above the tip of the abdomen. They then walked backward
up the stem, and thus pushed out the mass as they came to the top.
Often they used the hind legs to assist in getting it out of the way,
sometimes kicking it to a little distance. Once in every two or three
trips they would come out far enough to expose part of the thorax.
They appeared and disappeared with the regularity of a machine, never
stopping to rest.
We remained with them until seven o’clock, when we placed a long bottle
over each stem in such a way that while it did not interfere with the
work of the wasp, it caught the chips of pith as they fell out. At the
end of an hour we noted the amount of accumulation in the tube, and
thus had a measure of their rate of work. The drawing gives an idea of
the arrangement of the tube on the stem. When we left them they were
still digging and delving.
At half past nine we took a lantern and went down to visit our charges.
We expected to find them at rest, and asleep; but on the contrary
they were working as busily as ever, and upon examining the measuring
glasses we found that they had not paused since we left them. We
measured the depth of the débris in the bottles, and then emptied them.
At four o’clock on the next morning we went to the garden, and
were much surprised to find that the two wasps had worked without
intermission throughout the night. Indeed they seemed to have shortened
a little the time that it took to make a round trip down the gallery
and up to the opening again, since there was more pith in the bottles
than we could have expected if they had worked at only their former
rate. Neither the coolness of the air nor the darkness of the night
had made the slightest difference to them. After watching them a few
minutes, and marveling at their powers of endurance, we cleared out the
tubes and returned to bed. At half past eight we found them still at
work. Unlike us, they had taken no morning nap, but had gone on with
their tunneling in their usual steady way.
From this time their ways diverged, and they must be described
separately. At nine o’clock the one that we had first seen came up to
the opening, walking head first, and flew off, remaining away seven
minutes. When she returned she at once resumed her work, and kept at
it without a pause until two in the afternoon. At this hour she went
away, and we never saw her again. We suppose that she was killed, for
it seems improbable that so faithful a creature could have deserted her
half–finished home. Pompilus quinquenotatus often deserted a partly
finished nest for some more enticing spot, and Sphex started several
excavations before making a final choice; but we cannot believe that
there was anything fickle about Crabro.
The second wasp came up head first to the entrance of her hole at
two minutes after nine, as though she had been influenced, in some
subtle way, by her neighbor’s example; but after looking about for a
moment she went back. She repeated this observation several times, and
finally, at twenty–five minutes after nine, came out and flew to a leaf
near by. Then she circled around, alighting a number of times, and at
last departed. Her stay was brief, for at just thirty–five minutes
after nine she returned, and at once settled down to her work.
We now began to make notes as to the length of time that it took her
to go down and bring back her load. We timed her again and again, and
found that she was remarkably regular, each of her trips occupying from
forty–five to fifty seconds.
All that day we kept her under strict surveillance, and never once did
she suspend her operations either for rest or refreshment. Late in the
afternoon, while we sat watching her as she appeared and disappeared
with almost the regularity of clockwork, we found it difficult to
realize that the patient little creature had been at work for more than
twenty–four hours, with only one brief intermission. Without hurry or
flurry she kept at her task, reminding us, in her business–like ways,
of the social wasps of the genus Vespa. When we left her, at dusk, we
attached the recording tube to the stem, and at ten o’clock in the
evening we found that she had not stopped working. We emptied the
glass, and left her.
At seven o’clock in the morning of July twenty–ninth we paid her a
visit, and could scarcely believe the testimony of our senses when we
saw that the record was one of unceasing toil through the long hours
of the second night. We began to wonder if she would ever finish her
task. Wonderful though she was, we had grown a little weary of our
long session of watching. We had been glad that she worked through the
first night; it was creditable to her and interesting to us, and we
admired her even more for sticking to it through the second, but when
it looked as though we might have to remain by her side through another
long day, watching an endless series of loads as they were carried out,
we confess that we thought she was rather overdoing it. Gradually,
however, she slowed up her work, taking two or three minutes to make a
journey down and up. At last, at just nine o’clock, her head appeared
at the top of the stalk, and after a slight hesitation she flew away.
The nest was completed.
We have studied wasps for a number of years, and we feel that we are
on terms of more or less intimacy with many of the species, but never
before have we known one to work after day was done. We have often
gone out with a lantern at bedtime for a tour of inspection among our
nests, and have always found the inhabitants quiet and presumably
asleep. The social wasps are very industrious, but during the hot
nights of July they are to be seen clustered together on the outside
of their paper nests in deep repose; and although the Vespa wasps
that nest in the ground sometimes come home late in the twilight, we
have never seen them work after it was really dark. Polistes fusca
may be said to share our cottage, so thickly does she hang her combs
under the shelter of our porches, and from observations taken at all
hours we know that she is quiet through the night. Sir John Lubbock, in
“Ants, Bees, and Wasps,” speaks of the great industry of wasps. He has
known them to work from early morning until dusk without any interval
for rest or refreshment; but here was our little Crabro toiling from
three in the afternoon of July twenty–seventh, through that night
and the day and night following until nine o’clock on the morning of
the twenty–ninth,—a period of forty–two consecutive hours with one
intermission of ten minutes on the morning of the twenty–eighth. Surely
she takes the palm for industry, not only from other wasps, but from
the ant and the bee as well.
[Illustration: NEST OF C. STIRPICOLA]
The nest was completed, but the work of storing it remained to be done.
The wasp flew away at nine o’clock, and ten minutes later came back
with something, we knew not what, for she dropped into her hole so
quickly that she was out of sight almost before we knew she was there.
Two minutes later she came up, and was off again. This time she was
gone twelve minutes, and when she returned we were again baffled in our
effort to see what she was carrying. When she came out she alighted
upon a leaf and attended to her toilet, cleaning both body and wings by
rubbing them off with her hind legs, and from this time on she never
started on a hunting expedition without paying this attention to her
personal appearance. On her third trip she was gone twenty minutes,
coming back with a small fly; and before we left her at ten o’clock,
she had stored six more. When we came back at half past two in the
afternoon she was working, and she kept up her goings and comings until
four o’clock, when she suspended operations for the day. On the next
morning we were called away, and know nothing of what she did, but on
the following day, Thursday, we resumed our observations. She worked
hard all the morning, but in the afternoon her trips were few, and were
made at long intervals. On Friday she worked from eight to nine, when
she departed, and never returned. We watched for her, at intervals,
all through that day and the next, when we were forced to conclude that
our faithful little worker had fallen a victim to some bird or beast.
We did not disturb the nest until four days later, when we cut the
stalk, and examined it.
We found that the tunnel was thirty–nine centimeters in length. This
was a long distance for her to excavate, and, all things considered,
her progress had been rapid. We have opened a number of stems that had
been stored by this species, and all the excavations were from thirty
to forty centimeters in length, the width of the gallery being about
three and one half millimeters, while on each side there was from one
to one and one half millimeters of pith that had not been cut away. Of
course these points varied with the diameter of the stem and also with
the size of the worker.
Our little stirpicola had stored one cell, had laid an egg, and had
built a partition of pith across the stem as a floor to the second
cell, before her untimely taking off. Had she lived, ten or twelve
cells would have been stored, one above the other. The completed cell
contained a larva and parts of eighteen flies of different sizes, four
species being represented. The flies had all been attacked by the
larva, the abdomens of some and the thoraces of others having been
eaten. The larva continued to eat for two days, and then spun its
cocoon. The flies found in this and in other nests of stirpicola were
all dead. All the pupæ that we kept wintered in the cocoon and came out
in the spring.
[Illustration: AMMOPHILA SLEEPING IN THE GRASS (AFTER BANKS)]
The females of Crabro, like those of other genera, seem to use their
galleries as sleeping places, but the males stop at any convenient
inn. We once entertained one of them for several nights in a hole in
one of the posts of our cottage porch. Other males, as in Philanthus,
spend time and care in digging a hole in the ground, to which they
return night after night. In Agenia the female keeps one cell ahead
of her needs, and tucks herself away in it very comfortably; but the
Pelopæi, instead of making this use of their tubes, congregate in the
evening where there are convenient crevices, and make as much fuss
about getting settled as a lot of English sparrows. Mr. Banks has
made a delightfully pretty as well as interesting observation on the
sleeping habits of Ammophila. In a corner of his garden where the grass
grew long, dozens of these wasps arrived every evening, and after a
good many changes in position, fell sound asleep, clinging to the stems
about one third of the way down. They registered at this hotel between
seven and eight o’clock, and departed before five in the morning. We
have seen a Pompilus take the greatest care in selecting a sheltered
spot under some leaves, where she afterward hung herself up, and
slept soundly until after eight the next day; and Mr. Brues has found
companies of Priononyx atrata passing the night on the stems of sweet
clover.
Chapter VI
AN ISLAND SETTLEMENT
OUR children often made themselves useful by reporting finds in the
shape of nests, and one day they returned from the island with a
wonderful tale of great numbers of big wasps that were digging in the
ground. “I don’t know what they are,” said the small boy, “but they act
to me like the maddest kind of hornets.” With this attractive picture
before us, we lost no time in going over to the spot, where we found
a thriving colony of Bembex spinolæ. On our approach they fell upon
us, “desire of blood, and rage, and lust of fight” in their mien, and
chased us to a distance, but without inflicting a single wound. This
temperance was not due to gentleness of disposition, but to the fact
that Bembex is not at all handy with her sting, her body being too
large and clumsy to curve and give the lightning stab as other wasps
do. With renewed courage we again approached them, more cautiously this
time, and soon learned that if we preserved an extremely composed and
dignified demeanor our presence on the field would be tolerated.
Bembex, like Philanthus, and some species of Sphex, lives in a sort of
semi–social state, a number of individuals occupying the same space
of ground, although each one has its separate nest. Bembex, however,
differs from these genera and from almost all of the solitary wasps in
her habit of feeding her young from day to day, or rather from hour to
hour, as long as it remains in the larval state. This difference in
her maternal cares as compared with those of other species results in
a less numerous progeny. The larva, for a period of two weeks, demands
constant attention from the mother, so that a second egg cannot be laid
until the first–born has gone into its cocoon, unless, indeed, she
feeds two larvæ at once, which does not seem probable. The season of
work is ten or twelve weeks, so that Wesenberg is probably correct in
allowing only five or six young ones to each mother for the summer.
In watching our wasps we found that the new nests were usually made
in the outskirts of the colony, which was thus continually extending
its limits. Like many other species, Bembex has great difficulty
in deciding just where to dig. Our Sphex made three beginnings
before finally settling down. The only Ammophila that we watched
from the beginning changed her place after working for ten minutes.
P. quinquenotatus often tried half a dozen places before she was
satisfied, and spinolæ is quite as difficult to please.
When, at last, the right place is found, the labor of excavation is
carried on vigorously. The mandibles are used for loosening the earth,
and for lifting, but the greater part of the work is done with the
first pair of legs, the tarsi of which are doubled up while the dirt is
swept out with the brush of stiff spiny hairs on the second joint. This
attitude gives them a very comical aspect, making them look as if they
were sweeping with their elbows. They sometimes lie far over to one
side while loosening the earth with their mandibles. While digging, the
body is held high by the straightening of the third pair of legs, and
the dirt comes out behind in a rapid stream, flying to a distance of
three or four inches. Before long the wasp is lost to sight, but every
few moments she comes backing out, pushing behind her the dirt that
she has displaced below. In about fifteen minutes the nest is ready,
and the wasp turns her attention to scattering all the dirt that has
been thrown out, sweeping the ground clean so that no sign of her work
remains. We have often speculated as to the meaning of the careful and
conscientious performance of this part of her task. With the wasps that
nest by themselves it is not easy to see what enemy they are providing
against in hiding the entrance to the nest; but the precaution seems
still less necessary—even absurd—in the Bembex field, where there is
no possibility of concealing the colony, and where the nests are only
an inch or two apart, so that an enemy might burrow anywhere with
the certainty of finding one. Moreover, the only enemy that we could
discover was the parasitic fly, which never attempts to enter when
the hole is closed. However, unmoved by our opinion on the subject,
spinolæ spends five or six minutes of her precious time in making the
neighborhood of her home quite tidy, and then she fills in the mouth of
the nest with a little loose earth before going away to catch her fly.
Oxybelus, though she is limited in choice by her small size, can
catch a fly in three or four minutes. Bembex is strong enough to take
anything that she sees, and she has no preference for one species
above another, yet she seldom finds one under twenty or twenty–five
minutes. When she comes back nothing of the fly is visible unless it
is unusually large, so closely is it held under her body by the second
pair of legs. She alights, and scratches away the loose earth at the
entrance of the nest with her first legs, and then, as she creeps
within, she passes the fly along from the second to the third pair, so
that the end of its body, projecting beyond the abdomen of the wasp,
is visible for an instant before it is carried inside. Sometimes she
drops the fly behind her, and then, turning around, pulls it in with
her mandibles. In other cases, where a longer portion of the tunnel has
been filled with earth, the fly is left lying on the ground while the
wasp clears the way. This offers a favorable opportunity to parasites,
especially as the fly is not placed with regard to its safety, but
is dropped anywhere. The dirt that is kicked out sometimes covers it
so that when the way is clear the careless proprietor must search it
out and clean it off before she can store it away. In one instance,
in which we had been opening a nest close by, the tunnel was entirely
blocked by the loose earth which we had disturbed, and the wasp worked
for ten minutes before she cleared a way to her nest. During part of
this time she held the fly, but when she realized that it was going to
be a long piece of work she laid it down near by. As the wasp enters
she sometimes leaves the hole open behind her, but oftener fills it by
pushing up earth from below. When she comes out again she throws in a
little dirt, and then begins to circle about the place. She seems not
quite easy about the nest, however, returning three or four times to
scratch earth over the entrance, before finally taking her departure.
We opened a good many nests in the course of the summer, and found
them all very much alike, much more so than is the case with other
species. The entrance tunnel runs in obliquely for from three to five
inches below the surface of the ground, and ends in a pocket.
We grow accustomed to marvels, and from our familiarity with other
wasps we take as a matter of course the unerring accuracy with which
Bembex swoops down upon the exact spot at which the entrance to her
nest is hidden. And yet how strange a power it is! There is not the
least sign to help her—not a stone, not a blade of grass is to be seen
on the field. Our method of marking a nest which we wished to find
again was to place tiny pebbles at exactly equal distances from it, one
on either side, so that the middle point of the straight line between
them gave us the desired spot; and the wasp doubtless uses the same
method, only her landmarks are sometimes so infinitesimal that we do
not recognize them.
Bouvier finds that when he cuts away the plants around the nest of B.
labiatus, clearing a space of twenty–eight or thirty inches square,
the wasp is much confused, flying about for a long time before she is
able to find her home. He once placed a flat stone over the entrance.
The wasp alighted upon it, and after scratching vainly for a while made
her way in. The stone was left in this position for two days, during
which time Bembex learned to regard it as a landmark, for upon its
being removed to a distance of eight inches she still followed it upon
returning with her fly, and insisted upon finding her nest near it.
[Illustration: NEST OF BEMBEX]
An observation of Marchand points to the same conclusion. He says:—
On July seventeenth, 1900, during a short sojourn at Pouliguen, on
returning from a hunt after Diptera and Hymenoptera in the cliffs of
Caudan, about eleven in the morning, in tropical heat, I paused to take
breath near the old mill of Caudan and looked about for a little shade
before continuing my walk to Pen–Château. I had seated myself on the
stones of a slope shaded from the sun and was wiping the perspiration
from my forehead, when I saw a large wasp arrive directly before me. I
instinctively followed it with my eyes; it paused some yards from the
mill on the side of the cliff, and began to open a nest which was placed
scarcely twenty inches from the foot of a swallow–wort, a rather common
plant in the neighborhood of the ruin. She was Bembex rostrata at work
at provisioning her nest.
Moved by curiosity, instead of going on to breakfast, I awaited the exit
from the nest, which took place in about five minutes. Bembex scratched
the sand and took flight from the side of the cliff. How long would she
be away? I looked at my watch and arose.
Ought I to go or to wait a little while? I took the latter decision. Out
of malice, and without any idea of trying a control experiment to the
admirable observations which science owes to the naturalist of Sérignan,
of whom I was not thinking at all, I cut close to the sand the stalk
of the swallow–wort and planted it a little nearer the mill, moving it
about two feet, and being careful to put in place of the plant a little
fragment of a bottle which I found in the mill. I seated myself in the
shade and waited. Twenty minutes later the wasp dropped straight on to
the place where I had cut the plant, that is to say, it deviated from
its nest by a distance about equal to the displacement to which I had
subjected the swallow–wort. It walked right and left, agitating its
antennæ, appearing confused as to the locality. I followed these goings
and comings for two or three minutes. Several times it flew away and
then returned, always searching about. Pitying it and desiring, since I
was now relieved of the fatigue which the heat had caused me, to go back
to breakfast, I took my net and drawing near, made as if to catch it,
swinging the pocket rapidly about. It veered away with a quick jerk of
the wings. I then took up the swallow–wort, lifting the fragment which
marked its original place, and replanted it in the sand.
I again looked at my watch to see whether I could consecrate yet a
few more minutes to curiosity without making my kind host, my friend
Dr. M^[ce] Rivron, and his wife, who honored me with the charming
hospitality of Kursac, wait too long. It was only half past eleven; we
usually did not breakfast until about noon; it would take only a quarter
of an hour to traverse the distance from the mill of Caudan to the
house. I could then, without fear of being chided, dispose of fifteen
minutes. This lapse of time would perhaps suffice to show me whether my
_bestiole_ would this time find the way to her nest without hesitation.
I waited a little; five minutes had not passed when my Bembex, coming
like an arrow, alighted on the sand near the plant, still holding the
prey which I had noticed when she departed at my chasing her, after
her vain attempts to find the entrance to her nest; but this time she
did not hunt long. She felt about a little to right and left, but soon
turned directly toward the entrance to the tunnel, distant scarcely two
inches from the place where she had settled. My Bembex had a memory.
A curious thing about these wasps, and one which shows how much common
feeling they have, is that they work in waves, all starting off on
their hunting expeditions within a few minutes of each other, and
returning together after the chase. At one time all the residents seem
to be present, digging their nests, carrying in their booty, dashing
at each other, and chasing the parasites with a tremendous amount of
humming and swooping about. Then suddenly they are all gone. Nothing
remains but multitudes of flies, which keep up a giddy dance over the
field, and for ten or fifteen minutes the place seems deserted. Then
the wasps begin to return, several coming at a time, and as if by magic
the whole scene awakens to life. More than half of the wasps bring
nothing home with them, and these fall to robbing their more fortunate
companions. Those that are carrying flies must pause a moment, burdened
as they are, to scratch away the earth at the entrance to the nest.
When unmolested they go in very quickly, but it is just at this point
that the marauders fall upon them, displaying an amount of persistence
and energy in their attacks that, were it properly directed, might
easily enable them to secure flies for themselves.
We once saw a wasp that had been fortunate enough, or perhaps
unfortunate enough, to catch an immense fly, the wings of which stood
out on both sides very conspicuously. This made her an especial mark
for her unprincipled relatives. Half a dozen of them chased her about,
like chickens pursuing one of their number that has found a worm. She
circled and settled, and circled and swooped around for five or six
minutes, continually pursued and attacked by the robbers, and quite
unable to get into her nest. At last, curious to see what she was
carrying, we made her drop her load, and secured it for ourselves.
We found it to be a horse fly, quite dead, but showing no marks of
violence. It was not wasted, for we afterward fed it to one of our wasp
nurslings at home.
At another time we saw one wasp attack another that was bringing in a
fly. In the struggle that ensued the owner lost her booty, as the two
rolled over and over on the ground, and as they parted it was seized by
the thief. They clinched again, and rolled on the ground as before, and
this time the fly was recovered by the rightful owner. At this point,
thinking that perhaps one of the wasps was a male, and that this might
be their style of courtship, we seized both of them; whereupon the fly
was dropped, and the two wasps turned their attention to attacking us.
Both proved to be females. Not only do the Bembecids fight in this way
for the possession of their prey—they quarrel even without apparent
cause. We have seen two females digging their nests at a little
distance apart, one of which was repeatedly attacked by the other,
although she did nothing to provoke the aggressor. They are certainly
very unneighborly, and have no idea of living in harmony. When flying
in a threatening manner, either at us or at each other, they have a way
of wagging their abdomens violently from side to side in a way well
calculated to inspire terror.
In warm sunny weather spinolæ works industriously through the middle
of the day, and seems determined to provide abundantly, not only for
her own offspring, but for any unbidden guests that it may be her
fate to care for. She never works more than four or five hours a day,
however, and in unfavorable weather she does not work at all. On going
over to the island one cloudy morning to spend some hours in watching
the Bembex activities, we found the spot quiet and lifeless. No one
seeing it for the first time would have dreamed of the multitudes of
living creatures beneath his feet. The nests seemed to be all closed,
but on peering curiously about we found one on sloping ground, in the
suburbs of the colony, of which the door was open. Just within was
the proprietor gazing out on the landscape, as she is shown in the
illustration. She seemed to be leaning on her elbows, and her face,
enlivened by two great goggle eyes, had an irresistibly comical
aspect. With the exception of the omnipresent flies, this wasp was
the only sign of life about the place. Even in good weather, and in
working hours, the wasps sometimes rest, for we have seen them go in
empty–handed, closing the door behind them, to remain for half an hour
at a time.
[Illustration: BEMBEX SPINOLÆ LOOKING OUT OF NEST]
There is one thought that must strike even a casual observer at the
sight of the hordes of parasites that hover over a Bembex colony:—
“The buzzing flies, a persevering train,
Incessant swarm, and chased return again.”
Why do not these wasps, fly–catchers as they are by profession, kill
the worthless wretches that infest their homes, thriving abundantly on
the fruits of their labor, a continual menace to the life and safety
of their offspring? To the uninitiated it would seem that these flies
might serve as food for the wasp larvæ quite as well as any of the
dozen species that they actually take; but even if the wasp–mother
believes that they possess indigestible qualities, it would be much
less trouble to kill them and throw them away than to be perpetually
chasing them to a little distance only to see them return as soon as
she gives her attention to anything else. Whatever the reason for it
may be, the relation between the wasps and the flies is certainly most
curious and puzzling. Fabre’s explanation is that since this miserable
little fly has its own part to play in nature, Bembex must respect it,
thus preserving harmony in the world of living things. The idea is
perfectly in accord with his own theories, but we find ourselves quite
unable to accept it.
There can be no doubt that the parasites are a grave danger to Bembex.
She suffers from them far more than any other wasp that we are
familiar with, her mode of feeding the young rendering her peculiarly
susceptible to their attacks. Of the ten or twelve nests that we
opened only one was free from them, the others containing from two
to five lively maggots nearly as large as the wasp larvæ, which were
sharing the food brought in by the mother. Fabre, who has studied the
question thoroughly, has found as many as ten parasitic larvæ in one
nest. He has also noticed that where the parasites are most numerous
the wasp–larva is proportionately small and emaciated, reaching only
one half or one third of its normal size. When it attempts to spin
its cocoon it has not strength enough to do so, and thus perishes
miserably among the pupæ of the interlopers, which have the advantage
of developing more rapidly. He has proved, by experiments upon nests
transported to his study, that although the invaders preserve friendly
relations with the rightful owner of the nest so long as food is
abundant, they nevertheless, at the first suggestion of scarcity, fall
upon the wasp larva and ruthlessly devour it. This “black action” he
has seen with his own eyes. In view of this base ingratitude, we are
more than ever impressed with the troubles of the poor Bembex mother,
as she tries to feed a dozen mouths where she has bargained for only
one.
We several times saw a fly follow a wasp into her nest, remaining
within for half a minute, and it is probable that they go in to lay
their eggs. According to Fabre, it is the habit of the flies that are
parasitic upon the half–dozen species of Bembex that he has studied
to seize the moment at which the fly projects from under the abdomen
of the wasp as she enters the nest; and he has even known them to lay
two or three eggs on one fly in the instant of time that its body was
exposed.
Fabre took a partly grown Bembex larva from the nest, where it was
surrounded by the remains of twenty flies. He fed it generously, and it
ate sixty–two more, making a total of eighty–two in the eight days that
passed before the spinning of the cocoon. Our experiments in this line
gave similar results. We took charge of a partly grown larva on the
afternoon of August tenth, and between that date and August fifteenth,
when it spun its cocoon, it ate forty–two house flies besides a big
Tabanus.
Fabre thinks that under natural conditions the mother does not give
the larva all it can eat at one time, but provides it with what she
considers a reasonable amount of food, and keeps anything that she
catches beyond this out of its reach. He draws his conclusion from the
fact that he has found several flies in the tunnel leading to the nest,
while the larva had as many more close to it. It would certainly be
convenient for Bembex to have a reserve of this kind in case of rainy
weather, but the forethought implied in such an action seems to require
a higher degree of intelligence than can be claimed for her.
In one nest we found a single fly with a long cylindrical egg attached
to the left side of the thorax just at the origin of the third leg. In
another, which we had seen made and provisioned, we found, six days
later, a larva which we judged to be four days old. Assuming that the
egg was laid on the first day, it must have taken it about two days
to hatch. Other nests gave us larvæ in all stages of development,
surrounded by the remains of Diptera, among which Syrphus, Tabanus, and
Musca were represented.
In regard to the condition of the flies captured by Bembex, we have
never seen the crushing of the thorax, which is noted by both Wesenberg
and Fabre. Indeed, the flies that we found were not always dead, since
in two instances they responded readily to stimulation. Similar results
have been obtained by Mr. S. W. Dunning of Hartford, Connecticut.
Twice we have seen our spinolæ, as she was bringing home her prey,
alight near the nest and sting it as it was held with the second pair
of legs. We could see the process distinctly, since she is slow and
clumsy, and, in one instance, had difficulty in reaching the fly,
falling over to one side in an awkward manner. It is probable, then,
that this is a habit with the wasp, but that the sting is usually given
at the place of capture.
We opened a number of Bembex nests, but succeeded in raising only one
larva, which we took when it was half grown. This one, during the five
days that passed before it spun the cocoon, ate forty–three flies.
Mr. Bates has some notes on Monedula signata, which takes nothing but
flies, and even confines itself to a single species, although it must
sometimes go half a mile away to find it. This reminds us of Pompilus
quinquenotatus, which never takes anything but Epeira strix.
[Illustration: BEMBEX]
A considerable contribution to our knowledge of the genus Bembex has
been made in the paper by Wesenberg (written in Danish) which has
already been referred to. This paper deals with Bembex rostrata. It was
translated for Mr. Ashmead by Mr. Martin Linell.
[Illustration: A CORNER OF THE BEMBEX COLONY]
It seems that rostrata makes its nest in solid sand, covering it up
with loose sand, and usually, also, with a little flat stone, to
prevent parasites from entering. The cell measures one cubic inch, the
entrance tunnel being one and one half centimeters long, and arcuate. A
cell contains four or five fresh flies (Lucilia, Eristalis, etc.), and
torn–off wings, sucked–out thoraces, and in the middle of these, a big
flat larva.
When the larva is hatched the mother brings more and more flies, the
flies being larger and larger as it grows. This adjustment of the size
of the fly to the growth of the larva has also been noted by Fabre.
Wesenberg says that fifty Bembecids will nest on a spot as big as
a room during a period of three months. The time required for the
development of the larva is two weeks, this giving five or six young
ones for the season. He queries, “Does each female have more than one
nest? and if so, how can she remember them?” To determine this point
we marked six wasps by touching them with differently colored paints,
putting near their nests pebbles painted to correspond with the owners,
and then watched them closely for three hours. During this time the
red wasp returned regularly to the red nest, the blue to the blue, and
so on. They were watched for an hour and a half on the following day
with the same result, so that it seems quite certain that spinolæ has
only one nest at a time. To feed two larvæ at once, with interlopers
thrown in, would be a heavier task than the most determined industry
could accomplish.
Chapter VII
THE BURROWERS
DUFOUR, in describing the fearful ravages of Cerceris ornata among the
bees, says that the wasps of this genus are among other insects what
eagles and hawks are among birds. While this characterization does not
seem to fit the American species, it is certainly true that the genus
stands out as one of those in which the distinctive peculiarities
are strongly marked. They might be considered the aristocrats in the
world of wasps, their habits of reposeful meditation and their calm,
unhurried ways being far removed from the nervous manners of the
Pompilidæ or the noisy, tumultuous life of Bembex. Their intelligence
is shown by their reluctance to betray their nests, and by their
uneasiness at any slight change in the objects that surround them.
It is not necessary to attempt to catch them or to make threatening
gestures, in order to arouse their sense of danger. If you are sitting
quietly by a nest when the wasp opens her door in the morning she will
notice you at once, and will probably drop out of sight as though she
resented your intrusion into her privacy. After a little she will come
up again and will learn to tolerate you, but at the least movement on
your part, almost at the winking of an eyelid, she will disappear.
[Illustration: NEST OF CERCERIS NIGRESCENS]
Our four representatives of this genus all prey upon beetles that
are injurious to vegetation, and therefore deserve the gratitude of
agriculturists. Nigrescens, with her pale grayish bands, is a very
trying wasp to deal with. We had seen her flying about in the garden
for weeks before we succeeded in tracking her home, and when we did
succeed she was so late about getting up in the morning, stayed away
from home so many hours at a time, and went to bed so early in the
afternoon, that we were not well repaid for watching her nest all day.
Fumipennis, large and handsome, with a broad yellow band at the front
of the abdomen, is another wasp that has no regard for the convenience
of the people who are watching her. You may sit by her big open hole
for hours without seeing her, and when she comes she drops in so
suddenly that, unless you are very much on your guard, you are not sure
even then what she is. Clypeata and deserta are better subjects for
study.
The nests of our species are all deep, tortuous, and very difficult
to excavate. We have never succeeded in finding their pockets; and
yet, for various reasons, we feel perfectly certain that all of them
are like C. ornata in provisioning, successively, a number of cells
which lead out of the main gallery. When one of these cells is filled
with food, and the egg deposited, it is probably closed up, and thus
separated from the runway. From our experience late in the season
with the nests of another wasp, we are inclined to think that we made
a mistake in looking for pockets at the lower end of the tunnel. Had
we searched higher up, at the point of the curve, we might have found
them, the lower part of the gallery probably being designed merely for
a dwelling–place for the mother of the family.
[Illustration: CERCERIS CLYPEATA]
But although we did not get distinct pockets, there was, in at least
one nest, a supply of food that would have far exceeded the wants of a
single larva. We did not succeed in finding eggs on different groups of
beetles; but from a nest into which the wasp was still carrying food we
took a half–grown larva which was identified as being hers. The fact,
too, that a wasp occupies a nest for so long a time as ten days or two
weeks points to the conclusion that she uses it for a number of eggs
which are laid at intervals.
Cerceris digs her nest, deep as it is, all at once. In this she is
a contrast to her near relatives of the genus Philanthus, who busy
themselves for an hour or so every morning with fresh excavations.
On the eighth of July the weather was so warm and bright that we went
down to the garden at half past eight o’clock, knowing that it was
rather early, but hoping that the hot sunshine would tempt the wasps
to industry. We had walked up and down several times, when suddenly,
right in the pathway, a nest appeared. A great quantity of loose earth
had been taken out and heaped up, probably on the preceding day, and
in the midst of this a little hole had been opened since we passed
before. The place looked so promising that we sat down to watch it,
and a few minutes later we were rewarded by a glimpse of some antennæ
down the gallery, and then a little face with yellow markings appeared
but quickly vanished. Now followed a very coquettish performance. The
wasp came slowly creeping up again and again, only to drop out of sight
as soon as she had reached the opening. After a time she grew bolder,
and sat in her doorway, twitching her head this way and that in a very
expressive manner, as though she were planning the work of the day; but
it was plain that although she was up early, business cares were not
weighing heavily upon her mind, for forty minutes passed before she
came out of the nest, and after making three or four circles about the
spot, flew away.
How much livelier and more interesting it would have been if we could
have followed her! We tried to guess at what she was doing, and
imagined her hunting industriously. After fifteen or twenty minutes
it seemed to us that she must have caught something, and that she was
surely returning. Most probably she was not working at all, but was
breakfasting leisurely and exchanging compliments with her neighbors;
for when she did come home after keeping us waiting for an hour and a
half, she brought nothing with her, and seemed quite unconscious of
the fact that greater things had been expected of her.
We had placed a stone upon a dead leaf near by, to mark the
neighborhood of the nest, thinking that even a Cerceris could not
object to so simple an arrangement of natural objects; but our wasp
noticed it at once, and evidently with much suspicion and disapproval.
She began by circling several times just above it. Then she alighted on
it and examined it carefully, walking over it, and creeping underneath,
perhaps to see whether it in any way menaced the safety of her nest,
perhaps as the completion of a locality study made the day before.
She then rose on her wings, and after a little more circling, dropped
suddenly into her hole.
So far we had not been getting on very rapidly, but from this time
things took a turn. Cerceris is never in a hurry, and yet she may be
relied upon to do a certain amount of work every day. The one that we
were now watching had probably come back for a final look at her newly
made nest before beginning to provision it; for she soon reappeared,
and this time really went to work, since in forty minutes she brought
home a beetle which she carried by the snout, venter up, in her
mandibles, supporting it with the second pair of legs while flying. She
was much annoyed at our presence, and circled about as before. Twice
she alighted near by, and walked around for a few minutes, and when she
did this all her feet came down to the ground, the beetle being allowed
to hang loosely. At last she made the best of a bad matter, and went
in. The rest of the morning was occupied with hunting, the capture of
each beetle taking about forty–five minutes. Every time that she came
home she spent fifteen or twenty minutes in the nest.
This species soon became very common, and for two weeks scarcely a
morning passed without our finding at least one newly–made nest. The
study of clypeata, however, consumes a great deal of time. For example,
we found, one morning, two nests within six inches of each other.
It turned out afterward that these were inhabited by two different
wasps; but at the moment we supposed that one of them had been dug and
deserted and then a second one made, and wishing to know which one was
occupied we resolved to watch and see. After waiting for three hours we
saw one wasp returning; but upon noticing us she veered off and began
to circle about. She was heavily laden, and her burden, instead of
being supported by the second pair of legs, as is sometimes the case,
hung down under the thorax and abdomen. After a moment she alighted on
a plant near by, and seemed to consider the situation, then circled
a little more, and flew away, remaining out of sight for fifteen
minutes, then another return, more circlings and hesitations. She
seemed to feel the weight of the beetle now, and alighted frequently
on the ground and walked about; yet she would not go in, so reluctant
was she to betray her nest. In this way she kept us waiting for a whole
hour, although we were not very near to her, and were as still as
statues. At last we retreated, and stood as far back as we could and
still keep the hole in view. She now came closer, and, after hanging
poised on her wings for a moment, dropped into her nest.
We once found a nest of this species in process of construction. A
large heap of fresh earth had been pushed out, which entirely covered
the spot; but at intervals there were upheavals from below which
betrayed the presence of the wasp. When we saw it first it was half
past eight o’clock, and we judged, from what had been accomplished,
that she must have been at work at least an hour. It was half past
nine before the excavation was complete. We had not been certain, up
to this time, as to what we were watching; but now we had the pleasure
of seeing her open her doorway from below and stand in the entrance
while she washed her face with her fore feet, like a cat. When they
rest at the mouth of the hole the first legs, which are yellow, are
bowed in a semicircle on each side of the yellow face, the distal
joints being bent up so that the wasps seem to be standing on their
elbows. This attitude, which is often seen in Bembex spinolæ, gives
them a delightfully amusing, bow–legged appearance. They usually open
their nests in the morning at about nine o’clock,—a little earlier
or later according to the time at which the sun strikes the spot.
Then they spend from forty minutes to an hour in taking a survey, the
least movement on the part of a watcher causing them to drop out of
sight as if the earth had given way beneath them. Sometimes there is
a little way–station an inch or two within the tunnel, and the wasp
falls back only to this point, and here she may be seen, if one peeps
in cautiously, either quietly awaiting the retreat of the intruder, or,
perhaps, performing her toilet in a leisurely and elegant manner.
Whenever she leaves her nest she makes three or four rapid circles
around the spot to freshen her memory of the locality. The most
thorough study that we saw made by clypeata was in the case of the wasp
mentioned before, that was so long in carrying her beetle in because
of our being on the ground. When she finally did go in she stayed only
an instant—just long enough to deposit her load—and then came out and
spent a long time in an investigation of all the surrounding objects,
flying in and out among the plants, now high, now low, and circling
again and again around the spot. It looked as though she had been
puzzled and disturbed by the presence of unaccustomed things. As soon
as the survey was over she went inside and closed the door, as though
its object had been not so much to strengthen her memory as to correct
former impressions.
The work of bringing in beetles goes on very irregularly, and as a rule
not more than two or three are stored in the course of a day. It is
not unusual for clypeata to spend three or four hours away from home
and then come back without anything; and often, even in the middle of
the day, she passes an hour or two in the seclusion of her nest. We
had several nests under observation for a week at a time without ever
once seeing the owners, although they were evidently occupied, since
they were sometimes open and sometimes closed. The outer entrance is
always left open when the wasp goes away, although possibly access
to the pockets may be barred below; but when she enters she closes
the door unless she means to come out again at once. The closing is
sometimes effected by pushing the earth up backwards, with the end of
the abdomen; but the hole is rather too large for this method, and
more frequently the wasp comes up head first, carrying a load of earth
in her front legs. This is placed just within and to one side of the
entrance, and then more armfuls are brought up, until, after two or
three trips, the opening is entirely filled.
We once captured the wasp in a bottle, as she returned, loaded, to the
nest. She dropped the beetle, but soon picked it up again and stung it
vigorously, _with intention_, as the French say, first under the neck,
and then further back, behind the first pair of legs. After this it was
dropped while the wasp fluttered about for a few minutes, but it was
then picked up again, and stung as before. We both saw this operation
repeated in exactly the same way, four different times, with intervals
of five or six minutes between.
In a nest which we excavated after watching it for nine days, we found
nothing until we had gone six inches down, and at this point the
tunnel was lost; but mixed with the crumbly earth that we took out of
the hole, we found eight beetles and a half–grown larva of clypeata.
The destruction of this nest was accomplished one morning, and when
we came back to the spot twenty–four hours later we found that a new
one had been made close by, doubtless by the same individual. We had
expected to find her bringing beetles and dropping them foolishly on
the ground like Paul Marchal’s Cerceris ornata, and were gratified that
she showed an advance in intelligence over that species, although to
be sure she would have been still wiser had she chosen an entirely new
neighborhood. Another individual was so much disturbed by our scrutiny
that she dropped her beetle at the entrance to her nest. She did not
pick it up again and utilize it, although it lay for three days in the
dust at the threshold.
As to the condition of the beetles stored by clypeata: in the first
nest that we opened we found eight, seven of which were dead, while
the eighth, which we had just seen stung several times, was alive, but
died on the following day. The second nest gave us five beetles, all of
them dead and dry. In the other nests that we opened we found nothing,
though we knew that the beetles were there had we only been skillful
enough to discover them.
Of Cerceris deserta, which closely resembles clypeata, but appears
later in the season, we had only a single example. We chanced to see
her dropping into a crevice among some lumps of earth, and at first
could scarcely believe that this was the dwelling–place of a wasp, as
there was nothing whatever about it to indicate a nest; and even after
we had removed the rough pieces of earth above, we could see nothing of
the loose material that must have been carried out.
She was much like clypeata in her manners, with the same habit
of surveying the world from her doorway, and manifesting the same
annoyance at our presence when she was returning to the nest; but she
carried in more beetles in the course of the day and worked much more
rapidly. Between nine and eleven o’clock one morning she brought in
five loads, and some of the journeys occupied only ten minutes.
[Illustration: CERCERIS DESERTA: LOCALITY STUDY BEFORE LEAVING NEST]
The first time that she found us sitting by her nest she circled about
for nearly an hour, seeming unable to make up her mind to enter. At
length we withdrew a little way, but still her suspicions were not
entirely allayed; and after a further study of the situation she
dropped, not into her own nest, but into a large cricket hole near
by. Taken aback by this manœuvre, and thinking that perhaps we had a
second individual to deal with, we stealthily approached, and peering
in, could see the cricket inside, the wasp having slipped beyond. It
did not seem possible that the little creature could be endeavoring to
deceive us, and yet what other explanation could be offered for her
conduct? We again took up our distant position, and after ten minutes
more had the satisfaction of seeing the wasp slip out of the false nest
and drop instantly into the true one. After a little she became quite
accustomed to us, and entered her nest without the least delay.
The prey of deserta is held in the mandibles, and while we were
watching her she did not support it with the second legs, even when
flying.
Philanthus punctatus is a pretty little yellow–banded species much
resembling Cerceris in appearance. The nest consists of a main gallery
with pockets leading from it, each pocket being stored with one egg and
enough bees to nourish a single larva. When the wasps emerge from the
cocoon they find themselves in the company of their nearest relatives
and in possession of a dwelling–place, and they all live together for
a time before starting out independently to seek their fortunes. On
the fifth of August we discovered on the island a happy family of this
kind, consisting of three brothers and four sisters, the females, with
their bright yellow faces and mandibles, being handsomer than the
males. They seemed to be on the most amicable terms with each other,
their only trouble being that while they were all fond of looking out,
the doorway was too small to hold more than one at a time. The nest
was opened in the morning at about nine o’clock, and during the next
thirty or forty minutes their comical little faces would appear, one
after another, each wasp enjoying the view for a few minutes with many
twitchings of the head, and then retreating to make way for another,
perhaps in response to some hint from behind. Then one by one they
would come out, circle about the spot, and depart, sometimes leaving
one of their number to keep house all day alone. They usually left the
hole open; but when there was a wasp within, it was soon closed from
below. During this playtime period they did not return until they were
ready to settle down for the night, the first one coming home at half
after two or three o’clock, and the others arriving at intervals, none
of them staying out later than five. Most commonly they found the right
spot without trouble, scratched open the hole, and then either closed
it behind them or stood waiting in the doorway for the next arrival;
but occasionally they had difficulty in locating the nest, and worked
at two or three different places before finding it.
We kept these wasps under close observation, often watching the nest
from the moment it was opened in the morning until it was closed
at night. On the twelfth of August, a week from the time that we
first saw them, one of the females felt the responsibilities of life
settling down upon her. At half after four in the afternoon she began
to enlarge the nest, and worked with a great deal of energy for forty
minutes. After a long disappearance within the hole she would come up
backwards, kicking behind her a quantity of earth which was not only
taken outside, but was then spread out far and wide. She worked with
the front pair of legs, which were curved inward, after the manner
of Bembex; and when a pebble or some such object came in her way she
either dragged it to a distance with her mandibles or pushed it before
her with her head in a way quite peculiar to herself. In distributing
the earth that was taken out, she went five and one half inches
from the nest—a distance which is much greater than is common among
wasps, but which accords well with the habits of punctatus, since she
continues the work of excavation from day to day.
[Illustration: PHILANTHUS PUNCTATUS]
On August thirteenth, at half after eight in the morning, we found
that a second female, perhaps inspired by the example of her sister,
had made a new nest within two inches of the first one, and had flown
away, leaving it open. Presently the other wasps began to appear, one
after the other, in their doorway. Two of the males flew away, and one
of the females, doubtless the one that we had seen digging the night
before, began to work afresh at making the nest larger. Probably she
was excavating a pocket for the reception of an egg, and the amount
of labor required was enormously increased by the great length (about
twenty–two inches) of the main gallery by which the displaced earth
must be carried out. She worked for an hour, and in spreading the dirt
about, inadvertently filled in the opening of the second nest. At
length she flew away.
At ten o’clock a female arrived carrying a bee, and tried to find
nest No. 2. She came to the wrong place, and worked about, here and
there, for some minutes, holding the bee under the thorax, clasped by
the second pair of legs. Being unsuccessful, she dropped her burden,
and flew away for a few minutes. While she was gone we removed a leaf
that had fallen over her nest, and on her return she at once descended
upon the right spot, and began to scratch open the entrance, the bee
being kicked backward with the rejected earth. When the way was clear,
however, she picked it up, brought it toward the hole, dropped it, ran
in and out, brought it nearer, ran in again, and turning around in
the tunnel, seized the bee in her mandibles and pulled it down. This
performance was due to the accidental obstruction of the gallery, for
we afterward found that punctatus ordinarily flies directly into her
nest, or, when it is closed, pauses on the wing to scratch an opening
with the first legs. The bee is pushed backward a little as she goes
in, but does not often project from under her abdomen.
At fifteen minutes after ten the worker from nest No. 1 brought in a
bee, and from that time the two worked industriously. They showed some
individuality in their ways, for No. 2 always closed her door when she
went away, and never circled at all, while No. 1 invariably circled
before leaving, and always left her nest open. To be sure, there was
a female left on guard, so that perhaps she did not feel the need of
caution.
Our wasps had not far to go for their victims. Forty feet away, on
the eastern side of the island, was a steep declivity, and here, in
the soft crumbly soil, was a great Halictus settlement. No prettier
sight can be imagined than is presented by this colony on every sunny
summer day. The whole bank is riddled with nests, and at the entrance
of each stands a female bee, her tiny head exactly filling the opening.
The bees are constantly arriving, laden with pollen, whereupon the
sentinels politely back inward to make way for them. Into this scene of
contented industry descends the ravaging Philanthus, taking guards and
workers alike.
On the afternoon of the fourteenth of August our two wasps were in
the full tide of affairs. No. 1 took in eleven bees within two hours,
but her record was somewhat confused, as two other females were going
in and out at the same time. We felt sure that neither of these was
hunting, but one of them shared in the labor of the nest by helping
with the work of excavation.
No. 2, however, was alone, so that we could keep a definite account of
her comings and goings. We watched her from half past one until five,
at which hour she came home without a load, and at once closed the nest
for the night, after having stored thirteen bees in three hours and
nine minutes. In some cases the capture of the bee occupied only one,
two, or three minutes, while at other times she was gone much longer.
At each return she stayed only an instant—just long enough to deposit
the bee—inside the nest, and then spent a minute in carefully closing
the hole. The wasps that were going in and out of nest No. 1 sometimes
closed it when they went away, but this was done in an untidy fashion,
quite different from the nicety and precision of No. 2.
At half after five o’clock the wasp that had been digging for some
little time at nest No. 1 flew to nest No. 2, opened it, and attempted
to enter, but was quickly driven out by the owner. She then dug a
little in several other places, finally returning to sleep in the
family home. On the next day we found that No. 2 was tolerating in her
nest one of the females that had not yet begun to hunt, but whether it
was the one she had rejected the night before or the fourth member of
the sisterhood, we could not tell. On the eighteenth, three days later,
the wasp had left this temporary home and made a nest for herself four
feet away on the hillside. The males were still living in the first
nest with two females.
When the weather was cold and cloudy punctatus remained closely housed
within the nest, or, at most, came out to do an hour’s digging, and
then disappeared. The warmer the weather, and the more brilliant the
sunshine, the more rapidly they worked. When leaving the nest they
would often creep out and walk around it three or four times before
rising on their wings, and even then would sometimes alight once or
twice before flying away. The males, especially, liked to stand about
for a time, watching their more industrious sisters at their work. The
females usually began the day with digging, and frequently closed it,
toward night, in the same way.
In order to see the method of stinging, we at one time provided
ourselves with a number of bees, and putting one of them into a bottle,
introduced a wasp. She seized it almost immediately, with great vigor,
and stung it once, under the neck, and then dragged it up and down the
bottle by one antenna which was held in the mandibles. After a moment
she shifted it and held it with the second legs in the usual way. We
now put in another bee, which she also caught, stung in the same place,
and then dropped without relaxing her hold of the first one. As she
seemed to have nothing further to show us we released her, and after
circling a little she took into her nest the bee that she was carrying.
In our next experiment we used a larger glass, thinking that with more
space we might see malaxation. The instant that the wasp was introduced
she grasped the bee with one rapid powerful motion, and stung it
just under the neck as before. Then holding it with the second legs
she began to fly about in the glass. We now introduced another bee,
whereupon the first one was relinquished, and the second was treated
in exactly the same way. The stinging was the beginning and the end of
the operation, and when we released her she at once took the bee into
the nest. There was no malaxation outside, and certainly there was none
within, as was shown by the rapidity with which the wasps issued from
the nest after storing the bees. We were successful in getting the
wasps to sting only when we tried the experiment with those that were
hunting. When those that had not yet begun to store their nests were
put into the glass they paid no attention to the bees.
The victim of the sting of punctatus is killed at once. Life is extinct
from the instant that the stroke is given. This is true also of the
honey–bee that is the victim of Fabre’s Philanthus apivorus; but the
explanation that he gives of the action of his wasp in thus dealing
sudden death instead of paralyzing its foe—that the honey must be
sucked out of the bee before it can be safely used as food for the
larva—does not hold good in our case, since the honey that Halictus
carries to mix with the pollen upon which her offspring are fed, is not
removed.
[Illustration: NEST OF PHILANTHUS PUNCTATUS
A–B, 3½ inches; B–C, 5 inches; C–D, 14 inches; D–E, 8 inches]
As time went on we found on the island two other Philanthus colonies,
although that is rather too large a word to apply to them, since one
consisted of four nests and the other of only two. When we came to
excavate the nests of this species we were greatly astonished at the
length of the gallery, and not until then did we properly appreciate
the industry of these little wasps. It is no small undertaking to
follow one of their tunnels for twenty–two inches, even when, as in
this case, the greater part of it is parallel to the surface of the
ground. We did not find distinct pockets, as the soil was very crumbly
and fell in as we worked, but we came upon clumps of bees an inch or so
to one side of the gallery and about three inches apart, with larvæ in
different stages of development. In one nest we found twenty–six bees
in two clumps, some of them half–eaten, and some of them fresh, but
all quite dead. We have no doubt that punctatus completely provisions
one pocket and closes the opening from it into the gallery, before she
starts another, making a series of six or eight independent cells.
The provision for one larva is probably twelve or fourteen bees, the
capture of which, in good weather, would be a fair day’s work.
That the males do not always stay on in their ancestral home is shown
by an observation that we made on the only occasion that we ever saw
this species in our garden. Nothing was stirring at half past three
o’clock in the afternoon, and we had given up work and started for
home, when, in going up an inclined part of the field, we noticed
something in motion within a ragged–edged hole which ran obliquely into
the ground. It seemed strange that a wasp should be beginning its nest
at so late an hour; but a wasp it was, as we could plainly see when we
took an attitude sufficiently humble. It was loosening the earth with
its mandibles, and then pushing it backward with its hind legs and
abdomen. We had scarcely settled down to watching it when a second one
of the same species appeared, and with a good deal of fuss and flutter
began to dig its hole close by. The spot chosen by this second one
proved unsatisfactory, and another beginning was made in a new place.
Again something was wrong, nor was a third choice any better. At last,
however, the work was started in earnest, and might have been carried
to a conclusion if we had not caught the little creature to satisfy a
suspicion that had been growing in our minds. Yes, we were right. The
worker was not a female making a nest for the rearing of her young, but
a male punctatus, preparing a shelter for the night.
In the mean time the first wasp had pushed back such a quantity of
earth that the hole was entirely closed, but every few minutes he came
backing out to clear the way. At the end of half an hour all became
quiet. The door remained closed, and doubtless the wasp was fast
asleep. Putting a blade of grass and then an inverted tumbler over the
nest, we left him for the night.
On removing the glass at half past seven the next morning, we found
the nest open but the wasp not visible. At half past eight the head
appeared just inside the hole, the long antennæ twitching now to this
side, now to that, as if an inspection were being made. Soon the head
came out. The wasp stood for some minutes making a survey, looking
to right and left with lively jerks of the body. Then, apparently
concluding that the day was not far enough advanced, he came out,
whirled around, and ran head–first into the nest. He probably took
another nap, for all was quiet until just before ten o’clock, when the
antennæ appeared again. The survey was taken as before, first from
within and then with the head in view. At last he flew out, and making
three circles, each one wider than the last, about the place, flew
away. He stayed out all day, and had not returned at half past three in
the afternoon; but on going down at half past four we found that he had
gone in and closed the door from below.
It is clear, then, that these males do not construct a new lodging
every night, but return to the same spot to sleep. Other wasps creep
into crevices. We have often found them, in the morning, in the holes
of the posts of our cottage porch; but we are glad to be able to put
it down to the credit of one male that he has sufficient foresight and
industry to provide a sleeping–place, and sufficient intelligence to
return to the spot when the declining sun warns him that evening is
approaching.
While punctatus was in the height of its activity we found another
species, P. ventilabris, taking bees of several genera and species
into a ground nest. She also carried her prey with her second pair of
legs, and whenever she left her nest she closed the door. She was a shy
little thing, and did not approve of our interest in her. At one time,
being startled by some movement on our part, she dropped her load and
flew away. We placed the bee upon the closed nest, and when she came
back with another, she paused and looked at it, took in the one she
was carrying, and then returned for number one. This was placed on the
threshold while she entered and turned around, and was then pulled in.
Some wasps, notably C
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