WASPS

SOCIAL AND SOLITARY

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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

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.

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CONTENTS

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LIST OF ILLUSTRATIONS

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.

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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.

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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.[ill11]

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.

[ill19]

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.

[ill-27]

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.[ill-27]

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.

[ill31]

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.

[ill39]

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?”

[ill59]

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.

[ill61]

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.

[ill63]

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.”

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. [ill75]

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.

[ill79]

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.[ill81]

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.

[ill85]

WASP HOMES IN THE LOG CABIN

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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.[ill89]

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.[ill91]

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.

[ill99]

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.

[ill103]

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.[ill106]

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.[ill-107]

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.[ill113]

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.