Chapter X

Chapter XTHE ENEMIES OF THE GRASSHOPPEREARLY in September a little black Tachytes suddenly became very common in the garden. The first one that we saw was going forwards in a series of long jumps, carrying a small grasshopper which was held by the base of the antennæ. She soon doubled on her tracks, and it became evident that she did not know her way; but after going about in circles for two minutes she ran into her nest. When she came out she spent a long time in circling around, flying close to the ground in wavy, snaky lines, occasionally alighting to run a few steps; but in spite of this locality study, ten minutes later, when she came jumping along with her second grasshopper, she had lost her nest again and hunted about just as before, twice going directly over it without seeing it. While she was thus occupied another wasp of the same species attacked her and tried to get possession of the grasshopper, but the rightful owner was able to defend it. At last it was stored away,and she proceeded to fill the nest, scratching the earth in with her first legs and working it down with the tip of the abdomen. She worked quietly but steadily for ten minutes, closing the place neatly, and then brought bits of leaf and pieces of earth to cover it all over.ill249TACHYTESOn the same afternoon we saw another of these wasps digging her nest, but she was so much disturbed when we came anywhere near her that we were obliged to retire. On the next day we saw her astride of a small grasshopper, jumping along like the one of the day before. She too had great trouble in finding her way. When she reached the nest she laid her prey down while she went inside for a moment, and then, comingout, seized it by the antennæ and backed in with it, instead of taking it in forwards as was done in the other case.Another wasp of this species carried a much larger grasshopper, which was so heavy that she could not jump with it, but was obliged to keep to the ground. In this case only one was used instead of two, which is the usual number. This wasp was first seen at a distance of twenty feet from her nest, and yet she went straight to the right spot without the least confusion, showing that some individuals of the species have a better idea of locality than others.The nest is a short, shallow tunnel with an enlargement at the end, within which are placed the grasshoppers, on their backs, with their heads in. Earth is packed solidly into the tunnel, but not into the cavity at the end.We took two eggs of this species. Each was placed across the thorax of the grasshopper at the base of the neck, on the ventral side. Both hatched at the end of thirty-six hours from the time they were laid, ate for three days, and then spun their cocoons. One of them ate only one small grasshopper, leaving a second one untouched, while the other finished the large grasshopper that formed her sole provision.The grasshoppers taken from the nests, five in number, were in all cases alive, there being a quivering of the mouth parts, and in some cases of the legs also, without any stimulation. This condition lasted for twenty-four hours from the time the poison was injected. After that they became quiet, but remained alive until they were destroyed by the larvæ.ill251NEST OF TACHYTESIt is a curious thing that in these wasps is found the perfection of that method of paralyzing the prey which is so much dwelt upon by Fabre, although from their habits this fine workmanship is not of the slightest use to them. They entomb their victims underground, where the conditions are favorable to their preservation, and the extremely short period that elapses betweenthe laying of the egg and the spinning of the cocoon makes it a matter of indifference whether the grasshopper is alive or dead, since in any case it would be eaten before decomposition set in.We deserve no credit for discovering a second species, Tachytes peptonica, for by her loud buzzing, slow flight, and persistent hovering over the nest she gave us every assistance in her power. She looks and acts like one of the large leaf-cutting bees, and this resemblance is heightened by the fact that the grasshopper which she carries is frequently of a leaf-green color. Her nest, which is sometimes on the bare ground and sometimes in the grass, has no external sign to mark it, and when with a great deal of fuss and buzzing she descends and burrows, it closes behind her and disappears from view, so that unless one marks the exact spot there is no way of detecting it afterward. On her exit a very slight amount of scratching closes the hole and leaves it looking exactly like the surrounding surface; so that in comparing her work with the protracted labor of Ammophila and some species of Pompilus in disguising the locality of the nest, we were struck by the success to which she attained with a very trifling amount of effort.It takes peptonica thirty or forty minutes to catcha grasshopper, and at each visit she remains for ten or fifteen minutes inside the nest. The grasshopper is carried in the mandibles, supported by the second and third pairs of legs. We never succeeded in opening a nest of this species, but a grasshopper taken as the wasp was bringing it home did not die until the sixth day.In our summer work we often found ourselves wishing that we could be in half a dozen places at once and could chase several wasps at the same time. Never did we feel these desires more keenly than on the twenty-ninth of July, when, after spending the best part of an hour in watching the hunting of an Ammophila, we were obliged to choose between following her to a possible conclusion, and giving our attention to a little jet-black wasp, Lyroda subita, which we now saw for the first time. This wasp was running around a bunch of clover in a nervous, agitated manner, as though she were oppressed by some great anxiety. The chance of discovering something entirely new decided us to relinquish our Ammophiline hopes, and we sat down at the feet of our new teacher.We could not see anything remarkable about that bunch of clover, but certainly the spot had some strong attraction for the uneasy little wasp. She ran off first in one direction and then in another. She circled aboutand made short flights now this way and now that, but always returned. At last she betrayed the secret of her interest by descending to the ground and picking up a small black cricket which had been lying close by all the time. She flew up into the air with it, but even now did not leave the neighborhood, continuing to fly about from place to place, alighting now and again on the bean plants.After this performance had lasted for five minutes she brought her burden back to the same spot that it had occupied before, laid it down, and without vouchsafing to us any explanation of her conduct, began to burrow into the soft earth. She went down head first, backing out with the dirt, which she carried with the front legs. While she was thus occupied we defended her booty against two hunting parties of ants which, at different times, fell upon it and would certainly have carried it off if we had not been at hand.It took the wasp twenty minutes to open the burrow, although, as we afterward learned, it had been excavated before. At the end of that time she turned around inside, came out head first, and dragged the cricket within.We at once opened the nest, but found it impossible to follow the tunnel on account of the crumbling ofthe earth. Indeed, we almost concluded that we were doomed to complete failure, for it was not until we had gone down between six and seven inches that we found, in a little pocket, our wasp in company with three crickets, upon one of which was a larva a day or two old. At the time we knew nothing of the habits of Bembex spinolæ, and we were much astonished to find a wasp which evidently fed her young from day to day.The contents of the nest were carefully conveyed to our wasp-nursery at the cottage. The cricket that we had seen taken in was dead, as was also the one upon which the larva was feeding. The third one was alive, as was shown by a rhythmic movement of the palp on the right side. By the next day, however, this one also was dead.On the morning of the third day, July thirty-first, the larva had eaten all of the first cricket and the greater part of one of the others, leaving only the large hind legs. Supplying the place of the mother, we killed two more and put them into the tube. One of these was eight millimeters long, this being about the size of those which the wasp herself had caught, while the other was of another species and much larger, being thirty millimeters long. Its size and kind, however, made no difference to the larva, which attacked this one next, although there were two small ones yet untouched. It ate onlyhalf of this big one, however, and then passed on. On August second we gave it two more small crickets, and for that day and the one following its good appetite continued, but on August fourth it stopped eating. We thought that its larval life must be completed, and expected to see it spin its cocoon, but something was lacking which we were too ignorant to supply, and on August fifth it died. It had eaten six small crickets and half of the large one, which was equal to about two more. Thus ended our only acquaintance with this interesting little wasp.The second week of August furnished such good play in our garden that island life was neglected; but one brilliant morning we rowed over to the home of Bembex and Philanthus, hoping that something new was in store for us. We were not disappointed, for as we climbed the crest we met a splendid Chlorion cœruleum dressed in shining blue, cricket in mouth, plunging down the hillside through the long grass. Twenty-five feet below, she reached her underground home, vanished for two or three minutes, and then, coming to the entrance, turned her head from side to side as though listening. Some indiscreet insect was chirping loudly not far away, and before long the wasp ran out into the grass, flew to a stump, dropped to the ground, flew to the top of a tall weed, dropped again, and ran into a hole. A moment later she came out, dragging a very limp cricket. An ant that crossed her path was chased vindictively, and then the cricket was placed on its back and scraped from head to foot four or five times with the mandibles. She then ran a little farther, laid it down again, and repeated the operation, after which it was taken into the nest.ill257CHLORION AND THE INDISCREET CRICKET.To find ourselves on the track of a lively wasp at the beginning of her day’s work was great good luck, and as Madam Cœruleum was perfectly fearless and did her hunting on foot, instead of disconcerting us with the long flights by which many of our wasps made the chase hopeless, we had every chance to learn her ways.It was a fatal day for the crickets. Between nine o’clock and one, sixteen had been packed away, enough to provision three cells, as we knew from former observations. Her manner was brisk and energetic, as she ran about poking her head into every likely hole. At one time we saw her dislodge a cricket which tried to escape by hiding under some brush. She pursued, there was a lively scrimmage, and it was pulled out quite limp and was then held in the mandibles, back up, while she gave it a prolonged sting under the neck, after whichit was carried home without further manipulation. At another time she paused in her homecoming to give the victim one long squeeze at the neck. The crickets were placed in pockets, neatly arranged on their backs with their heads inward and their long legs projecting into the main tunnel. They were alive when taken, but died from day to day in the laboratory, the larvæ eating them in this state without criticism.While we were watching we noticed a much smaller wasp hovering about, and presently she slipped into the nest. When the owner returned and found her, there was a slight commotion in the passage-way, and then the inquiline appeared, shaking her wings in a flippant manner, as though she cared nothing for an encounter with the Big Blue. Instead of coming out immediately as usual, cœruleum stayed inside for twenty-five minutes. We should like to think that she was occupied in finding and destroying the egg of the parasite, but we have no reason to suppose that she could recognize that menace to her fortunes.Cœruleum lives in her nest and enlarges it from day to day to fit her necessities. On going over to the island one morning we found a cricket sleeping calmly in the entrance way, little guessing how dangerous was its position. It did not budge until the wasp came creeping upfrom below, when it jumped away to a place of safety. Before the day’s hunting began, a long study of the locality was made on foot, tufts of grass, weeds and stones being carefully noted, and this accounts for the ease with which the nest is afterward found.One July afternoon we saw a little red Tachysphex tarsata on the Bembex field of the island. She had a very anxious air, and was running about wildly and rapidly, holding a small grasshopper with the third pair of legs. She let it drop four or five times, and when she picked it up again she seemed to sting it, but of this we were not quite certain. At last she left it and began to rush about, investigating the Bembex holes, entering one of them and perhaps throwing out a little dirt as though she intended to use it, and then hurrying off to another. We have no doubt that her confusion was the result of her having lost track of a hole that she had made, as was the case with P. quinquenotatus in one of our earlier observations. The Pompilus, after a long search, resigned herself to the necessities of the case and made a new nest; but this little wasp could not adjust herself to a break in the system of her instinctive activities, and at last deserted her prey and disappeared. We waited for an hour; and then, as she did not return, we took possession of the grasshopper. It gave noresponse to stimulation and never revived, a very careful examination later showing that it was quite dead.On the next morning we again saw this wasp on the Bembex field. She was looking for a nesting-place, and when she had selected one she began to work; the weather was warm and sunny, so that the Bembecids were in the full swing of their obstreperous activity, and perhaps resenting the presence of the little red wasp, or perhaps in a spirit of teasing, they kept snatching her up and carrying her off to a distance of two or three feet. She took these interruptions with the most philosophic composure, hurrying back to her work as soon as she was released, without any display of resentment. When the nest was finished, she made a careful locality study both on foot and on the wing and then flew away. In twenty minutes she came back, apparently to refresh her memory, for she again made careful notes of all the points that could help her to identify the place. She dug a little more and then departed, to return five minutes later, on foot, with a grasshopper. In spite of all the precautions she had taken, at this exciting moment she was unable to remember just where her nest was, and spent some time in running wildly about, but when she did find it she went in without delay. We caught her as she came out, and dug up the grasshopper,but found no egg, so that she probably would have brought in a second victim had we let her go. The tunnel ran in obliquely for an inch and a half, the pocket at the end being two inches below the surface.A few days later we saw Larra quebecensis, another little grasshopper wasp, with the same red abdomen as tarsata, going to and fro about her nest, occasionally throwing out a little sand. She ran about near by all through the afternoon, but was not in a mood for work. On the next morning at ten o’clock, we found her touching up the nest a little, after which she left it open and flew away. In an hour she came leaping along like Tachytes, holding a small grasshopper in the third legs. This was placed inside the door while she turned around, and was then pulled in. She came out immediately, and in twenty minutes brought a second, and in ten more a third grasshopper, staying within this time for some minutes, after which she closed the nest. We took out the grasshoppers, one of which bore an egg underneath, in the middle, in front of the first pair of legs. The grasshoppers lived for five, six, and seven days, but the egg did not develop. We once saw a quebecensis that had laid down her grasshopper while she hunted for her nest. She was moving in sinuous lines up and down the face of a cliff, with incredible rapidity; wecould not distinguish her, but could see only a black streak with an occasional flash of crimson. When she rises on her wings, too, she is wonderfully quick, disappearing as if by magic, it being quite impossible to even guess at the direction she is taking.Chapter XIWORKERS IN CLAYTHE nests of Pelopæus cœruleus and Pelopæus cementarius, our two mud-daubers, are common under eaves and in other sheltered places, and many a country boy on opening them has been astonished to find that they do not contain wasps, but are crammed with spiders. Let them alone, however, and the wasps will arrive, for somewhere in the mass is an egg; and when it hatches the spiders will serve as breakfast, dinner and tea for the larva, until the change from the Arachnida to the Hymenoptera has been accomplished. Poor spiders! it is a wonder that there are any left, such thousands and tens of thousands are destroyed by these tremendously energetic enemies.Of what is Pelopæus thinking as, humming loudly, she jams her paralyzed and benumbed victims into her little cylindrical tubes? If only we could get inside of that little head! If only we could be wasps for a day, and then come back and tell about it, how much vain speculation would be saved! We can understand herwhen she soars gayly into the blue, the sunshine flashing from her brilliant wings; we too have felt the delight of health and freedom. She is still comprehensible when, at the close of day, she and her sisters quarrel for the favorite sleeping-places among the carvings of the porch pillars; but we cannot follow her mental processes when, at the moment of building, she surrenders herself to the mysterious sway of instinct, doing she knows not what, but doing it joyously, and preserving through it all the precious possession of her own individuality. Every aspect speaks of pleasure as these wasps gather at well or spring, and, singing contentedly, stand on their heads to gather their loads of mud. Briskly and gayly they fly back and forth, pausing at the nest long enough to pat the soft building material into shape. A single load makes half a ring at the larger part of the nest or a whole one at the bottom; and since one dries before the next is put on, the contour of each ring is visible when the tube is done, giving a very artistic effect. This is only accident, however; the wasp cares nothing about the beauty of the structure, for her next step is to daub the whole with lumps of mud, the walls being thus thickened and strengthened. About forty loads are necessary for each cell, and to build and provision one is a good day’s work.It is strange enough that with no one to teach her Pelopæus knew how to make her cell; but now she must do her hunting, and it is stranger still that she should be impelled to catch nothing but spiders. How does she know a spider from a fly, and why should she prefer one to the other? Not so unreasonable as some wasps, however, she demands nothing further than that her prey shall belong to this great group, and passes lightly over differences of species and genera. Her powerful sting fits her to cope with anything she may meet; but as the size of the cell must be taken into consideration, and the victim must be carried home on the wing, she is on the lookout for something not too large. Here then she ceases to be an automaton, and to some extent makes use of her wits.How does Pelopæus seize her spider? When and how many times is it stung? Is the wound given with discrimination, a certain point in the ganglion being pricked, so that the spider may be paralyzed, but not killed? Is there any malaxation?These were important questions to us, and we were therefore greatly excited over our first hunt. One of the blue wasps came flying along, alighted on our cottage wall, and began her search, creeping into corners and cracks and investigating cottony lumps of web.In a few moments a small Epeira strix (the only species to be found on the cottage) was dislodged, and at once dropped to the floor of the porch. The wasp paid no further attention to it, but went on with her search. Three more spiders, one after the other, were disturbed and dropped to the floor without being followed. The fifth one discovered was a little larger than the others, and was seized by the jaws and first legs of the wasp before it had time to escape. It was then rolled into a ball, or at least so it appeared, and stung, then rolled a little more and stung again, and then carried off. We had scarcely drawn breath after this performance when a second wasp appeared. This one dislodged two spiders, and then caught a third, which was seized and stung without any rolling, and then instantly borne away. A third wasp seized the first spider that she found, and started on her flight at the same moment, stinging it on the wing.So the game went on, while we waxed warm with the excitement and fascination of the chase. As the hours went by some of the yellow mud-daubers appeared, adding to the interest of the scene, although we could not see that their method differed in the least from that of cœruleus.Rarely did they succeed in catching a spider untilthey had dislodged two or three. Sometimes the spiders were followed as they dropped, and were caught on the floor, but oftener the wasp let them escape and continued her search on the wall. At the moment of capture we could see that she bent her abdomen under and inflicted a sting, but although we concentrated our attention on the point we could not be sure as to just what part was touched. It is our impression that this first sting was given anywhere, at random, with the object of producing a condition of temporary quiet in the victim, so that the next part of the operation could be carried on with deliberation.The second step in the procedure was commonly for the wasp to alight upon some neighboring object, usually the branch of a bush or tree, and sting the spider a second time, being evidently in no haste; but the difficulty of following her as she flew, and her habit of alighting above our range of vision, made it almost impossible to see just what she did. She certainly remained on the branch for some moments, either resting quietly or rolling the spider around and around, and had every opportunity to sting it as carefully as she wished; but we afterward found that she followed no exact method, since two thirds of the spiders were killed at the moment of capture, and most of the othersdied within a week, while a few lived for thirty-five or forty days. In this study we opened five hundred and seventy-three cells and handled over two thousand spiders, watching over them from day to day with a magnifying glass, that no sign of life might be neglected.When Pelopæus has filled her cell, she seals it up and makes another close to it, clusters of from six to twenty being found in one spot. Any especially desirable place is used by great numbers; and they make a lively scene, working eagerly at their nests, dashing off for more mud or bringing in their victims. All animated by the same compelling instinct, they are still individuals, and the character of each enters into her work. One picks up the first spider she sees, no matter how tiny it may be, and makes twenty-five or thirty journeys before her cell is filled, while another seems to have a calculating turn of mind, using four or five big spiders instead of a quantity of small ones. Has she made a note of the calibre of her cell, and determined to save herself trouble by looking farther and selecting the largest ones that will go in?ill271HORIZONTAL CELLS OF THE MUD-DAUBERMost of them place their cells vertically; but a few prefer the horizontal position, while still others, undecided as to the matter of direction, make clusters in which some are horizontal and others upright. Occasionallythere is a remarkable innovation in building-material, as where in a group of fifteen, four cells in the centre were constructed of pure white plaster, forming a striking contrast to the surrounding mud color. One wasp built an entire cluster after an original fashion, following the beaten track until the cell was completed, and even bringing mud enough to daub it over, as her sisters were doing, but sticking it all in one spot, so that when the group was complete irregular lumps were attached here and there, leaving visible the elegant architecture of the individual cells. Did she think they were too pretty to spoil? or was she merely one of those radical spirits that rebel against conventionality and demand change for the sake of change? It is these variations that furnish Natural Selection with its materials; but rigid as may be the rules regarding the non-survival of the unfit, we find that the race of Pelopæus still produces many absent-minded wasps, that after spending hours in carefully constructing their nests, seal them up empty, forgetting to put in the spiders or to lay the egg.When a cell is sealed, the mother wasp ceases to take an interest in it, but she has done all that is necessary. In two or three days the egg hatches, after which the larva spends ten or fifteen days in eating, and then spins its cocoon. Here it remains, perhaps for only a few weeks,—for there are two or three generations in one season,—or perhaps through the long months of winter.Fabre gives a most entertaining account of a French species of Pelopæus which nests in the wide-mouthed chimneys of the peasant. Undisturbed by the steam of washing day or the bustle of dinner-getting, the wasp enters the open door, passes unconcerned among the human inhabitants, and makes her cells against the smoky bricks, out of reach of the flames. This species kills her prey at the moment of capture, by which act she falls in the estimation of Fabre, who respects a wasp in proportion to the nicety with which she delivers her sting. He says, however, that at least she follows a logical method in turning to account these spiders, menaced with early decay. In the first place the prey is multiplied in each cell. The piece actually attacked by the larva is soon a disorganized mass, likely to decay speedily; but it is small and is consumed before decomposition can advance, for when a larva once attacks aspider it does not leave it for another. The others then remain intact, which is enough to keep them fresh during the short period of larval life. When, on the contrary, the prey consists of a single large piece, it is necessary that the organic life should be maintained, and a special art must also be observed in eating it. It is well then that Pelopæus is inspired to take numerous small pieces. The egg, moreover, is always placed on the first spider brought in, whether the storing of the nest is completed within a few hours, or whether, as in some cases, it occupies several days; and this M. Fabre considers a very happy arrangement.The French Pelopæi differ from ours at nearly every point. Ours kill only about two thirds of their victims, many of the others being paralyzed so perfectly that they live for two or three weeks. Again, ours, instead of placing the egg upon the first spider, almost invariably lay it upon the last one brought in. Another point of difference is that our larvæ frequently start in by eating up the soft abdomens, like children who first devour the plums in their pudding, returning later to the tough parts that are left, a rash and reprehensible course of action of which their better-taught French cousins are never guilty. When one comes to compare the two sets of facts furnished by the two groups of species, thedeductions which Fabre has drawn as to the importance of the instincts of the French group are seen to be unfounded. The American species violate nearly every principle which he considers necessary to their existence, and yet they flourish and multiply. For our part we find nothing in the actions of Pelopæus that needs to be explained—nothing that is not well adapted to the conditions under which each species works. The measure of praise or blame which we mete out to these depredators is merely a way of saying whether we would or would not follow their methods in provisioning our houses and rearing our children. Perhaps we would always use large spiders and would always have them fresh; but it is evident that tastes differ, and the matter is so purely a subjective affair that it will have to go unsettled. In any event, whether her victims be strong or feeble, old or young, big or little, fresh or dry, they certainly serve admirably in enabling Pelopæus to rear brood after brood, and to people the different parts of the earth with abundant representatives of her kind.Chapter XIISENSE OF DIRECTIONWE once made a number of experiments to discover in what way the social wasps came back to the nest on returning from their hunting expeditions. Were they endowed with some innate power which made memory of places unnecessary, and enabled them to fly in a straight line to any point they wished to reach, or did their return depend upon the more commonplace method of remembering the appearance of the country-side?One morning at half past eight, we placed a wasp cage over the opening of a yellow-jacket hole that had been closed since the night before, and caught fifty-five workers, after which the nest was again closed, one of us taking the cage out on to the lake, while the other remained to watch for their return.At seven minutes before nine, twenty of the wasps were liberated an eighth of a mile from shore near the end of the island. All, without exception, flew towardthe island and away from the nest. Whether they settled could not be determined. The boat was then moved an eighth of a mile beyond the island to the north, where, at ten minutes after nine, the remaining wasps were set free. They seemed a good deal confused, and flew in all directions. Many returned to the boat and alighted, but soon flew away again. Two that settled on the boat were knocked into the water; but they instantly rose and circled up into the air until out of sight.Of the fifty-five wasps that we set free, thirty-nine returned to the nest by ten o’clock, five of them belonging to the lot that flew to the island, since they soon found their bearings and came directly home, reaching the nest before the wasps of the second lot were liberated.Of the thirty-five wasps that were set free at the second point, at least twenty started in wrong directions. Adding these to the first twenty, we have left only fifteen that appeared to know where to look for their home, and yet thirty-nine reached the nest in a little more than an hour from the time the first wasps were set free.On another morning we caught thirty-eight workers and took them to a boat-house on the shore of the lake, in the second story of which was a large room with twogood-sized windows; one looked west over the lake and away from the nest, the other east toward the nest, and both were wide open. The west window was the brighter, but the other was light, the sun being on that side of the house.We placed the cage in the middle of this room and opened the door, stationing ourselves well to one side so as not to interfere with the movements of the wasps. They came out very naturally, pausing a moment before flying, and followed each other so slowly that we could easily see which window they went out by. Twenty-two flew through the west window away from the nest, and sixteen through the east toward the nest.At another time we took fourteen wasps from the nest of a different species and carried them seventy-three yards to the southeast. The cage was opened so that they could fly out in any direction they chose, and they all started in a straight line for the nest. Later on the same day, we took forty-five from this nest, and set them free one hundred and seventy-six yards to the south. Seven flew north toward the nest, twenty-one south, eight west, and seven east, while the other two circled around as they rose higher and higher, until they were lost to view. None in this experiment returned to take a fresh start.Again, we took twenty-three wasps three hundred yards southeast of the nest and liberated them in an open field; thirteen flew east or south away from the nest, seven west or northwest toward the nest, and four returned to the starting-place and seemed unwilling to venture out again.These observations show that the two species of wasps with which we experimented have no sense of direction in the form of a mysterious additional sense, nor yet in the form of a power by which they keep a register of the turns and changes in a journey and are thus able to retrace their way. Our cage was of wire, and so open that they could see all about, as we carried them from place to place; yet when they flew out, they most frequently started in a wrong direction and toward a point that we had not passed. In many instances, however, these wasps returned to the nest, and it seems highly probable that as they rose higher and higher into the air, circling as they went, they discovered some lofty treetop or other object that had before served them as a landmark, and that in this way they were able to make their way home. Bee-keepers know that if young workers which, in strong hives, pass the first ten or fifteen days of their lives in feeding the larvæ without going abroad, are taken out and set free only a shortdistance from home, they are unable to find their way back, and perish, while those that have passed beyond the nursing stage and have begun to do outside work may be carried long distances away and still readily regain the nest.With the solitary wasps we attacked the problem from the other end. We observed what the social wasps did in attempting to return to the nest; with the solitaries, we watched them when, after making the nest, they prepared to leave it to go out into the fields or woods in search of food or prey, thinking that the procedure of different species under these circumstances would afford a clue to the faculty upon which they depended to find their way about. If they were furnished with an innate sense of direction they would not need to make a study of the locality of the nest in order to find the way back, but if they were without this sense it would be only common prudence to take a good account of their bearings before going far afield.The sight of a bee or a wasp returning to its home from some far distant spot, without hesitation or uncertainty, is indeed marvelous. When we saw our first Ammophila perform this feat we were filled with wonder. How was it possible for her to hunt for hours, in all directions, far and wide, and then return in a directline to a nest which had been so carefully covered over that every trace of its existence was obliterated?To say that she is a creature of instinct, however, is not quite fair to her ladyship’s intelligence, as a better acquaintance with her would prove. In reading much popular natural history one might suppose that the insects seen flying about on a summer’s day were a part of some great throng which is ever moving onward, those that are here to-day being replaced by a new set on the morrow. Except during certain seasons the exact opposite of this is true. The flying things about us abide in the same locality and are the inhabitants of a fairly restricted area. The garden in which we worked was, to a large extent, the home of a limited number of certain species of wasps that had resided there from birth, or having found the place accidentally, had settled there permanently. To make this matter clear let us suppose the case of an individual of A. urnaria. In June she spent her time in sipping nectar from the onion flowers or from the sorrel that grew on the border of the garden. In July came the days of her courtship and honeymoon, and these too were passed in going from flower to flower, from one part of the garden to another. Many a day we have followed her when she flew from blossom to blossom along a row of bean plants, turning, whenshe reached the end, and wending her way leisurely back along the next row. Then comes a day when we see her running over the ground and looking carefully under the weeds for a good nesting-place. At last a spot is selected and she begins to dig; but two or three times before the work is completed she goes away for a short flight. When it is done, and covered over, she flies away, but returns again and again within the next few hours, to look at the spot and, perhaps, to make some little alteration in her arrangements. From this time on, until the caterpillars are stored and the egg laid, she visits her nest several times a day, so that she becomes perfectly familiar with the neighborhood, and it is not surprising, after all, that she is able to carry her prey from any point in her territory in a nearly direct line to her hole—we say nearly direct, for there was almost invariably some slight mistake in the direction which made a little looking about necessary before the exact spot was found.After days passed in flying about the garden—going up Bean Street and down Onion Avenue, time and time again—one would think that any formal study of the precise locality of a nest might be omitted; but it was not so with our wasps. They made repeated and detailed studies of the surroundings of their nests.Moreover, when their prey was laid down for a moment on the way home, they felt the necessity of noting the place carefully before leaving it.Of the species that catch their prey before making the nest we have good examples in Pompilus quinquenotatus, the tornado wasp, and fuscipennis, the Pompilus with the red girdle.ill283COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN FINDING HER SPIDER AND IN RETRACING HER STEPS TO THE NEST[5]The tornado wasp may make her nest anywhere from one to ten feet from the spot on which she has deposited her spider, while fuscipennis never goes more than fourteen inches away. During the process of excavation both of these wasps pay several visits to the spider, and frequently they have difficulty in finding it. As an example of this kind of trouble we give a diagram of the course followed by an individual of fuscipennis after she had finished her nest, in trying to find her spider and in bringing it home. This and the other similar diagrams that are given are reductions of large tracings that were made on the spot. Although not absolutely correct they are exact enough for all practical purposes, since wherever there is an error it is necessarily in the direction of making the path pursued by the wasp appear shorter and less complex than it really was. The individual in question had placed her spider on a cucumber vine which lay on the ground, not hidden by leaves, but fully exposed to view. The nest was only eight inches away, but when it was finished and the wasp went to bring the spider, she found it only after a search of three minutes; and then when she wentback to the nest she at first passed to one side and went some inches beyond, so that she had to retrace her steps.Marchal notes that some wasps are very unskillful in finding their way about, showing by their errors and hesitations not only that they have no sense of direction, but that they are badly served by their memory and by what senses they have. He draws this conclusion from his own observations, one of which had for its subject Pompilus seriaceus, which nests, conveniently for him, in the walls of the rustic summer-house which he uses for a laboratory. A wasp of this species, having caught her spider, had a most wearisome experience in getting it to the nest, which had been previously excavated near the ground. She first carried it straight up, not only passing the opening, but going to the very top of the wall. Realizing that she had gone wrong, she laid it down, and after a prolonged hunt up and down, to the right and to the left, found the nest; but on leaving it again to go for the spider, she started in exactly the wrong direction, down instead of up; and not until forty minutes had been spent in searching alternately for spider and for nest did she finally bring the two together.The best evidence that wasps depend upon a knowledgeof the place in returning to their nests is given by the pains they take to acquire that knowledge. When Sphex ichneumonea was ready to dig her nest, she had great difficulty in finding a place that suited her. Many a spot was merely looked at and passed by, while others that seemed more attractive were left after they had been excavated for a little way. At last, the nest dug, she was ready to go out and seek for her store of provisions; and now came a most thorough and systematic study of the surroundings. The nests that had been partly made and then deserted had been left without any circling. Evidently she was conscious of the difference and meant, now, to take all necessary precautions against losing her way. She flew in and out among the plants, first in narrow circles near the surface of the ground, and now in wider and wider ones as she rose higher in the air, until at last she took a straight line and disappeared in the distance. Very often, after one thorough study of the topography of her home has been made, a wasp goes away a second time with much less circling or with none at all.If the examination of the objects about the nest makes no impression upon the wasp, or if it is not remembered, she ought not to be inconvenienced nor thrown off her track when weeds and stones are removedand the surface of the ground is smoothed over; but this is just what happens. Aporus fasciatus entirely lost her way when we broke off the leaf that covered her nest, but found it, without trouble, when the missing object was replaced. All of the species of Cerceris were extremely annoyed if we placed any new object near their nesting-places. One Ammophila refused to make use of her burrow after we had drawn some deep lines in the dust before it. The same annoyance is exhibited when there is any change made near the spot upon which the prey of the wasp, whatever it may be, is deposited temporarily. We learned from experience how important it was not to disarrange the grass or plants on such occasions. The wasps are in many cases so prudent as to conceal their booty among the leaves; and this made it very inconvenient to keep our eyes upon the captured prey, as was quite necessary if we wished to follow it on its travels. To avoid the discomfort of lying on the ground or of twisting the neck at some impossible angle for half an hour at a time, we sometimes gently moved the intercepting objects to one side; but even such a slight change cost us dear in time and patience, as it threw the wasp out of her bearings and made it difficult for her to recover her treasure. We recall one exceedingly warm day in September when we weredelayed in this way for forty minutes, when she would have seized the spider and gone on her way without a pause had we not interfered.ill288LOCALITY STUDY OF ASTATA BICOLOR[6]Very often the wind would shake the plant so that the spider or caterpillar would fall to the ground. Under these circumstances the wasp was not at all disconcerted, but, on not finding her prey where she had left it, dropped at once to where it was lying. This is probably only an extension of their ordinary habits. A wasp that takes spiders learns to follow them as they drop from the web on being disturbed. In this they are evidently guided by sight, but perhaps they are also aided by the sense of smell under other conditions,—to the extent, at least, of recognizing the place upon which their prey has lain. With so much to build upon, it is easy to see how natural selection may have perfected the habit. We are delaying a long time over details, but we feel that to invoke an unknown sense is permissible only after a careful study of the daily life of the animals in question has left the problem unsolved.ill289LOCALITY STUDY OF ASTATA UNICOLOR[7]Among the wasps that first make the nest and then provision the larder, Astata bicolor is one of the most interesting. She makes a permanent abiding-place, and probably uses it until all of her eggs are laid. It is evident that since she comes and goes many times during the several weeks of her occupation, she does not need to make a prolonged study of the environment at every departure. Her first survey, just after the nest is completed, is most thorough; and, as a usual thing, when she first comes out on each succeeding morning, she reviews the situation more or less carefully. Individuals differ in this respect, however, some studying their local habitat much more than others. In this as well as in all other matters our observations are in complete accord with those of Sir John Lubbock, who says: “Indeed, many of my experiences seem to show not only a difference of character in the different species of ants, but that even within the limits of the same speciesthere are individual differences between ants, just as between men.”[8]This little bug-hunting Astata bicolor made her study in a different way from Sphex ichneumonea. She first flew from the nest to a spot near by and settled there, returning, after a moment, to the nest, or else flying to another resting-place. After pausing in a number of places (in the case of the one followed in the diagram, thirteen), she finished by a rapid zigzag flight. Another wasp of this genus, unicolor, differed from bicolor in not returning to the nest from the different resting-places, and inwalking from one to another of them instead of flying, although the last part of the study was made on the wing.ill290SECOND LOCALITY STUDY OF A. UNICOLOR[9]Cerceris deserta was one of the wasps that objected strongly to our presence, and she also made a great deal of fuss about leaving her nest. Nearly all the species circle before leaving a spot to which they intend to return, but deserta begins her flight with a series of short zigzags in the form of a half circle on one side of the nest. C. nigrescens, too, begins with semicircles, while C. clypeata flies entirely around and around theopening. The contrast between the deliberate movements of Astata and the rapid flight of Cerceris is very striking.We have now given a sufficient number of instances, from widely separated genera, to show the care that is taken by wasps to acquaint themselves with the surroundings of their nests. It has also been shown that in spite of all this care they frequently have trouble in finding their way about. All these facts have led us to conclude that wasps are guided in their movements by their memory of localities. They go from place to place quite readily because they are familiar with the details of the landscape in the district they inhabit. Fair eyesight and a moderately good memory on their part are all that need be assumed in this simple explanation of the problem.

THE ENEMIES OF THE GRASSHOPPER

EARLY in September a little black Tachytes suddenly became very common in the garden. The first one that we saw was going forwards in a series of long jumps, carrying a small grasshopper which was held by the base of the antennæ. She soon doubled on her tracks, and it became evident that she did not know her way; but after going about in circles for two minutes she ran into her nest. When she came out she spent a long time in circling around, flying close to the ground in wavy, snaky lines, occasionally alighting to run a few steps; but in spite of this locality study, ten minutes later, when she came jumping along with her second grasshopper, she had lost her nest again and hunted about just as before, twice going directly over it without seeing it. While she was thus occupied another wasp of the same species attacked her and tried to get possession of the grasshopper, but the rightful owner was able to defend it. At last it was stored away,and she proceeded to fill the nest, scratching the earth in with her first legs and working it down with the tip of the abdomen. She worked quietly but steadily for ten minutes, closing the place neatly, and then brought bits of leaf and pieces of earth to cover it all over.

ill249

TACHYTES

On the same afternoon we saw another of these wasps digging her nest, but she was so much disturbed when we came anywhere near her that we were obliged to retire. On the next day we saw her astride of a small grasshopper, jumping along like the one of the day before. She too had great trouble in finding her way. When she reached the nest she laid her prey down while she went inside for a moment, and then, comingout, seized it by the antennæ and backed in with it, instead of taking it in forwards as was done in the other case.

Another wasp of this species carried a much larger grasshopper, which was so heavy that she could not jump with it, but was obliged to keep to the ground. In this case only one was used instead of two, which is the usual number. This wasp was first seen at a distance of twenty feet from her nest, and yet she went straight to the right spot without the least confusion, showing that some individuals of the species have a better idea of locality than others.

The nest is a short, shallow tunnel with an enlargement at the end, within which are placed the grasshoppers, on their backs, with their heads in. Earth is packed solidly into the tunnel, but not into the cavity at the end.

We took two eggs of this species. Each was placed across the thorax of the grasshopper at the base of the neck, on the ventral side. Both hatched at the end of thirty-six hours from the time they were laid, ate for three days, and then spun their cocoons. One of them ate only one small grasshopper, leaving a second one untouched, while the other finished the large grasshopper that formed her sole provision.

The grasshoppers taken from the nests, five in number, were in all cases alive, there being a quivering of the mouth parts, and in some cases of the legs also, without any stimulation. This condition lasted for twenty-four hours from the time the poison was injected. After that they became quiet, but remained alive until they were destroyed by the larvæ.

ill251

NEST OF TACHYTES

It is a curious thing that in these wasps is found the perfection of that method of paralyzing the prey which is so much dwelt upon by Fabre, although from their habits this fine workmanship is not of the slightest use to them. They entomb their victims underground, where the conditions are favorable to their preservation, and the extremely short period that elapses betweenthe laying of the egg and the spinning of the cocoon makes it a matter of indifference whether the grasshopper is alive or dead, since in any case it would be eaten before decomposition set in.

We deserve no credit for discovering a second species, Tachytes peptonica, for by her loud buzzing, slow flight, and persistent hovering over the nest she gave us every assistance in her power. She looks and acts like one of the large leaf-cutting bees, and this resemblance is heightened by the fact that the grasshopper which she carries is frequently of a leaf-green color. Her nest, which is sometimes on the bare ground and sometimes in the grass, has no external sign to mark it, and when with a great deal of fuss and buzzing she descends and burrows, it closes behind her and disappears from view, so that unless one marks the exact spot there is no way of detecting it afterward. On her exit a very slight amount of scratching closes the hole and leaves it looking exactly like the surrounding surface; so that in comparing her work with the protracted labor of Ammophila and some species of Pompilus in disguising the locality of the nest, we were struck by the success to which she attained with a very trifling amount of effort.

It takes peptonica thirty or forty minutes to catcha grasshopper, and at each visit she remains for ten or fifteen minutes inside the nest. The grasshopper is carried in the mandibles, supported by the second and third pairs of legs. We never succeeded in opening a nest of this species, but a grasshopper taken as the wasp was bringing it home did not die until the sixth day.

In our summer work we often found ourselves wishing that we could be in half a dozen places at once and could chase several wasps at the same time. Never did we feel these desires more keenly than on the twenty-ninth of July, when, after spending the best part of an hour in watching the hunting of an Ammophila, we were obliged to choose between following her to a possible conclusion, and giving our attention to a little jet-black wasp, Lyroda subita, which we now saw for the first time. This wasp was running around a bunch of clover in a nervous, agitated manner, as though she were oppressed by some great anxiety. The chance of discovering something entirely new decided us to relinquish our Ammophiline hopes, and we sat down at the feet of our new teacher.

We could not see anything remarkable about that bunch of clover, but certainly the spot had some strong attraction for the uneasy little wasp. She ran off first in one direction and then in another. She circled aboutand made short flights now this way and now that, but always returned. At last she betrayed the secret of her interest by descending to the ground and picking up a small black cricket which had been lying close by all the time. She flew up into the air with it, but even now did not leave the neighborhood, continuing to fly about from place to place, alighting now and again on the bean plants.

After this performance had lasted for five minutes she brought her burden back to the same spot that it had occupied before, laid it down, and without vouchsafing to us any explanation of her conduct, began to burrow into the soft earth. She went down head first, backing out with the dirt, which she carried with the front legs. While she was thus occupied we defended her booty against two hunting parties of ants which, at different times, fell upon it and would certainly have carried it off if we had not been at hand.

It took the wasp twenty minutes to open the burrow, although, as we afterward learned, it had been excavated before. At the end of that time she turned around inside, came out head first, and dragged the cricket within.

We at once opened the nest, but found it impossible to follow the tunnel on account of the crumbling ofthe earth. Indeed, we almost concluded that we were doomed to complete failure, for it was not until we had gone down between six and seven inches that we found, in a little pocket, our wasp in company with three crickets, upon one of which was a larva a day or two old. At the time we knew nothing of the habits of Bembex spinolæ, and we were much astonished to find a wasp which evidently fed her young from day to day.

The contents of the nest were carefully conveyed to our wasp-nursery at the cottage. The cricket that we had seen taken in was dead, as was also the one upon which the larva was feeding. The third one was alive, as was shown by a rhythmic movement of the palp on the right side. By the next day, however, this one also was dead.

On the morning of the third day, July thirty-first, the larva had eaten all of the first cricket and the greater part of one of the others, leaving only the large hind legs. Supplying the place of the mother, we killed two more and put them into the tube. One of these was eight millimeters long, this being about the size of those which the wasp herself had caught, while the other was of another species and much larger, being thirty millimeters long. Its size and kind, however, made no difference to the larva, which attacked this one next, although there were two small ones yet untouched. It ate onlyhalf of this big one, however, and then passed on. On August second we gave it two more small crickets, and for that day and the one following its good appetite continued, but on August fourth it stopped eating. We thought that its larval life must be completed, and expected to see it spin its cocoon, but something was lacking which we were too ignorant to supply, and on August fifth it died. It had eaten six small crickets and half of the large one, which was equal to about two more. Thus ended our only acquaintance with this interesting little wasp.

The second week of August furnished such good play in our garden that island life was neglected; but one brilliant morning we rowed over to the home of Bembex and Philanthus, hoping that something new was in store for us. We were not disappointed, for as we climbed the crest we met a splendid Chlorion cœruleum dressed in shining blue, cricket in mouth, plunging down the hillside through the long grass. Twenty-five feet below, she reached her underground home, vanished for two or three minutes, and then, coming to the entrance, turned her head from side to side as though listening. Some indiscreet insect was chirping loudly not far away, and before long the wasp ran out into the grass, flew to a stump, dropped to the ground, flew to the top of a tall weed, dropped again, and ran into a hole. A moment later she came out, dragging a very limp cricket. An ant that crossed her path was chased vindictively, and then the cricket was placed on its back and scraped from head to foot four or five times with the mandibles. She then ran a little farther, laid it down again, and repeated the operation, after which it was taken into the nest.

ill257

CHLORION AND THE INDISCREET CRICKET

To find ourselves on the track of a lively wasp at the beginning of her day’s work was great good luck, and as Madam Cœruleum was perfectly fearless and did her hunting on foot, instead of disconcerting us with the long flights by which many of our wasps made the chase hopeless, we had every chance to learn her ways.

It was a fatal day for the crickets. Between nine o’clock and one, sixteen had been packed away, enough to provision three cells, as we knew from former observations. Her manner was brisk and energetic, as she ran about poking her head into every likely hole. At one time we saw her dislodge a cricket which tried to escape by hiding under some brush. She pursued, there was a lively scrimmage, and it was pulled out quite limp and was then held in the mandibles, back up, while she gave it a prolonged sting under the neck, after whichit was carried home without further manipulation. At another time she paused in her homecoming to give the victim one long squeeze at the neck. The crickets were placed in pockets, neatly arranged on their backs with their heads inward and their long legs projecting into the main tunnel. They were alive when taken, but died from day to day in the laboratory, the larvæ eating them in this state without criticism.

While we were watching we noticed a much smaller wasp hovering about, and presently she slipped into the nest. When the owner returned and found her, there was a slight commotion in the passage-way, and then the inquiline appeared, shaking her wings in a flippant manner, as though she cared nothing for an encounter with the Big Blue. Instead of coming out immediately as usual, cœruleum stayed inside for twenty-five minutes. We should like to think that she was occupied in finding and destroying the egg of the parasite, but we have no reason to suppose that she could recognize that menace to her fortunes.

Cœruleum lives in her nest and enlarges it from day to day to fit her necessities. On going over to the island one morning we found a cricket sleeping calmly in the entrance way, little guessing how dangerous was its position. It did not budge until the wasp came creeping upfrom below, when it jumped away to a place of safety. Before the day’s hunting began, a long study of the locality was made on foot, tufts of grass, weeds and stones being carefully noted, and this accounts for the ease with which the nest is afterward found.

One July afternoon we saw a little red Tachysphex tarsata on the Bembex field of the island. She had a very anxious air, and was running about wildly and rapidly, holding a small grasshopper with the third pair of legs. She let it drop four or five times, and when she picked it up again she seemed to sting it, but of this we were not quite certain. At last she left it and began to rush about, investigating the Bembex holes, entering one of them and perhaps throwing out a little dirt as though she intended to use it, and then hurrying off to another. We have no doubt that her confusion was the result of her having lost track of a hole that she had made, as was the case with P. quinquenotatus in one of our earlier observations. The Pompilus, after a long search, resigned herself to the necessities of the case and made a new nest; but this little wasp could not adjust herself to a break in the system of her instinctive activities, and at last deserted her prey and disappeared. We waited for an hour; and then, as she did not return, we took possession of the grasshopper. It gave noresponse to stimulation and never revived, a very careful examination later showing that it was quite dead.

On the next morning we again saw this wasp on the Bembex field. She was looking for a nesting-place, and when she had selected one she began to work; the weather was warm and sunny, so that the Bembecids were in the full swing of their obstreperous activity, and perhaps resenting the presence of the little red wasp, or perhaps in a spirit of teasing, they kept snatching her up and carrying her off to a distance of two or three feet. She took these interruptions with the most philosophic composure, hurrying back to her work as soon as she was released, without any display of resentment. When the nest was finished, she made a careful locality study both on foot and on the wing and then flew away. In twenty minutes she came back, apparently to refresh her memory, for she again made careful notes of all the points that could help her to identify the place. She dug a little more and then departed, to return five minutes later, on foot, with a grasshopper. In spite of all the precautions she had taken, at this exciting moment she was unable to remember just where her nest was, and spent some time in running wildly about, but when she did find it she went in without delay. We caught her as she came out, and dug up the grasshopper,but found no egg, so that she probably would have brought in a second victim had we let her go. The tunnel ran in obliquely for an inch and a half, the pocket at the end being two inches below the surface.

A few days later we saw Larra quebecensis, another little grasshopper wasp, with the same red abdomen as tarsata, going to and fro about her nest, occasionally throwing out a little sand. She ran about near by all through the afternoon, but was not in a mood for work. On the next morning at ten o’clock, we found her touching up the nest a little, after which she left it open and flew away. In an hour she came leaping along like Tachytes, holding a small grasshopper in the third legs. This was placed inside the door while she turned around, and was then pulled in. She came out immediately, and in twenty minutes brought a second, and in ten more a third grasshopper, staying within this time for some minutes, after which she closed the nest. We took out the grasshoppers, one of which bore an egg underneath, in the middle, in front of the first pair of legs. The grasshoppers lived for five, six, and seven days, but the egg did not develop. We once saw a quebecensis that had laid down her grasshopper while she hunted for her nest. She was moving in sinuous lines up and down the face of a cliff, with incredible rapidity; wecould not distinguish her, but could see only a black streak with an occasional flash of crimson. When she rises on her wings, too, she is wonderfully quick, disappearing as if by magic, it being quite impossible to even guess at the direction she is taking.

Chapter XIWORKERS IN CLAYTHE nests of Pelopæus cœruleus and Pelopæus cementarius, our two mud-daubers, are common under eaves and in other sheltered places, and many a country boy on opening them has been astonished to find that they do not contain wasps, but are crammed with spiders. Let them alone, however, and the wasps will arrive, for somewhere in the mass is an egg; and when it hatches the spiders will serve as breakfast, dinner and tea for the larva, until the change from the Arachnida to the Hymenoptera has been accomplished. Poor spiders! it is a wonder that there are any left, such thousands and tens of thousands are destroyed by these tremendously energetic enemies.Of what is Pelopæus thinking as, humming loudly, she jams her paralyzed and benumbed victims into her little cylindrical tubes? If only we could get inside of that little head! If only we could be wasps for a day, and then come back and tell about it, how much vain speculation would be saved! We can understand herwhen she soars gayly into the blue, the sunshine flashing from her brilliant wings; we too have felt the delight of health and freedom. She is still comprehensible when, at the close of day, she and her sisters quarrel for the favorite sleeping-places among the carvings of the porch pillars; but we cannot follow her mental processes when, at the moment of building, she surrenders herself to the mysterious sway of instinct, doing she knows not what, but doing it joyously, and preserving through it all the precious possession of her own individuality. Every aspect speaks of pleasure as these wasps gather at well or spring, and, singing contentedly, stand on their heads to gather their loads of mud. Briskly and gayly they fly back and forth, pausing at the nest long enough to pat the soft building material into shape. A single load makes half a ring at the larger part of the nest or a whole one at the bottom; and since one dries before the next is put on, the contour of each ring is visible when the tube is done, giving a very artistic effect. This is only accident, however; the wasp cares nothing about the beauty of the structure, for her next step is to daub the whole with lumps of mud, the walls being thus thickened and strengthened. About forty loads are necessary for each cell, and to build and provision one is a good day’s work.It is strange enough that with no one to teach her Pelopæus knew how to make her cell; but now she must do her hunting, and it is stranger still that she should be impelled to catch nothing but spiders. How does she know a spider from a fly, and why should she prefer one to the other? Not so unreasonable as some wasps, however, she demands nothing further than that her prey shall belong to this great group, and passes lightly over differences of species and genera. Her powerful sting fits her to cope with anything she may meet; but as the size of the cell must be taken into consideration, and the victim must be carried home on the wing, she is on the lookout for something not too large. Here then she ceases to be an automaton, and to some extent makes use of her wits.How does Pelopæus seize her spider? When and how many times is it stung? Is the wound given with discrimination, a certain point in the ganglion being pricked, so that the spider may be paralyzed, but not killed? Is there any malaxation?These were important questions to us, and we were therefore greatly excited over our first hunt. One of the blue wasps came flying along, alighted on our cottage wall, and began her search, creeping into corners and cracks and investigating cottony lumps of web.In a few moments a small Epeira strix (the only species to be found on the cottage) was dislodged, and at once dropped to the floor of the porch. The wasp paid no further attention to it, but went on with her search. Three more spiders, one after the other, were disturbed and dropped to the floor without being followed. The fifth one discovered was a little larger than the others, and was seized by the jaws and first legs of the wasp before it had time to escape. It was then rolled into a ball, or at least so it appeared, and stung, then rolled a little more and stung again, and then carried off. We had scarcely drawn breath after this performance when a second wasp appeared. This one dislodged two spiders, and then caught a third, which was seized and stung without any rolling, and then instantly borne away. A third wasp seized the first spider that she found, and started on her flight at the same moment, stinging it on the wing.So the game went on, while we waxed warm with the excitement and fascination of the chase. As the hours went by some of the yellow mud-daubers appeared, adding to the interest of the scene, although we could not see that their method differed in the least from that of cœruleus.Rarely did they succeed in catching a spider untilthey had dislodged two or three. Sometimes the spiders were followed as they dropped, and were caught on the floor, but oftener the wasp let them escape and continued her search on the wall. At the moment of capture we could see that she bent her abdomen under and inflicted a sting, but although we concentrated our attention on the point we could not be sure as to just what part was touched. It is our impression that this first sting was given anywhere, at random, with the object of producing a condition of temporary quiet in the victim, so that the next part of the operation could be carried on with deliberation.The second step in the procedure was commonly for the wasp to alight upon some neighboring object, usually the branch of a bush or tree, and sting the spider a second time, being evidently in no haste; but the difficulty of following her as she flew, and her habit of alighting above our range of vision, made it almost impossible to see just what she did. She certainly remained on the branch for some moments, either resting quietly or rolling the spider around and around, and had every opportunity to sting it as carefully as she wished; but we afterward found that she followed no exact method, since two thirds of the spiders were killed at the moment of capture, and most of the othersdied within a week, while a few lived for thirty-five or forty days. In this study we opened five hundred and seventy-three cells and handled over two thousand spiders, watching over them from day to day with a magnifying glass, that no sign of life might be neglected.When Pelopæus has filled her cell, she seals it up and makes another close to it, clusters of from six to twenty being found in one spot. Any especially desirable place is used by great numbers; and they make a lively scene, working eagerly at their nests, dashing off for more mud or bringing in their victims. All animated by the same compelling instinct, they are still individuals, and the character of each enters into her work. One picks up the first spider she sees, no matter how tiny it may be, and makes twenty-five or thirty journeys before her cell is filled, while another seems to have a calculating turn of mind, using four or five big spiders instead of a quantity of small ones. Has she made a note of the calibre of her cell, and determined to save herself trouble by looking farther and selecting the largest ones that will go in?ill271HORIZONTAL CELLS OF THE MUD-DAUBERMost of them place their cells vertically; but a few prefer the horizontal position, while still others, undecided as to the matter of direction, make clusters in which some are horizontal and others upright. Occasionallythere is a remarkable innovation in building-material, as where in a group of fifteen, four cells in the centre were constructed of pure white plaster, forming a striking contrast to the surrounding mud color. One wasp built an entire cluster after an original fashion, following the beaten track until the cell was completed, and even bringing mud enough to daub it over, as her sisters were doing, but sticking it all in one spot, so that when the group was complete irregular lumps were attached here and there, leaving visible the elegant architecture of the individual cells. Did she think they were too pretty to spoil? or was she merely one of those radical spirits that rebel against conventionality and demand change for the sake of change? It is these variations that furnish Natural Selection with its materials; but rigid as may be the rules regarding the non-survival of the unfit, we find that the race of Pelopæus still produces many absent-minded wasps, that after spending hours in carefully constructing their nests, seal them up empty, forgetting to put in the spiders or to lay the egg.When a cell is sealed, the mother wasp ceases to take an interest in it, but she has done all that is necessary. In two or three days the egg hatches, after which the larva spends ten or fifteen days in eating, and then spins its cocoon. Here it remains, perhaps for only a few weeks,—for there are two or three generations in one season,—or perhaps through the long months of winter.Fabre gives a most entertaining account of a French species of Pelopæus which nests in the wide-mouthed chimneys of the peasant. Undisturbed by the steam of washing day or the bustle of dinner-getting, the wasp enters the open door, passes unconcerned among the human inhabitants, and makes her cells against the smoky bricks, out of reach of the flames. This species kills her prey at the moment of capture, by which act she falls in the estimation of Fabre, who respects a wasp in proportion to the nicety with which she delivers her sting. He says, however, that at least she follows a logical method in turning to account these spiders, menaced with early decay. In the first place the prey is multiplied in each cell. The piece actually attacked by the larva is soon a disorganized mass, likely to decay speedily; but it is small and is consumed before decomposition can advance, for when a larva once attacks aspider it does not leave it for another. The others then remain intact, which is enough to keep them fresh during the short period of larval life. When, on the contrary, the prey consists of a single large piece, it is necessary that the organic life should be maintained, and a special art must also be observed in eating it. It is well then that Pelopæus is inspired to take numerous small pieces. The egg, moreover, is always placed on the first spider brought in, whether the storing of the nest is completed within a few hours, or whether, as in some cases, it occupies several days; and this M. Fabre considers a very happy arrangement.The French Pelopæi differ from ours at nearly every point. Ours kill only about two thirds of their victims, many of the others being paralyzed so perfectly that they live for two or three weeks. Again, ours, instead of placing the egg upon the first spider, almost invariably lay it upon the last one brought in. Another point of difference is that our larvæ frequently start in by eating up the soft abdomens, like children who first devour the plums in their pudding, returning later to the tough parts that are left, a rash and reprehensible course of action of which their better-taught French cousins are never guilty. When one comes to compare the two sets of facts furnished by the two groups of species, thedeductions which Fabre has drawn as to the importance of the instincts of the French group are seen to be unfounded. The American species violate nearly every principle which he considers necessary to their existence, and yet they flourish and multiply. For our part we find nothing in the actions of Pelopæus that needs to be explained—nothing that is not well adapted to the conditions under which each species works. The measure of praise or blame which we mete out to these depredators is merely a way of saying whether we would or would not follow their methods in provisioning our houses and rearing our children. Perhaps we would always use large spiders and would always have them fresh; but it is evident that tastes differ, and the matter is so purely a subjective affair that it will have to go unsettled. In any event, whether her victims be strong or feeble, old or young, big or little, fresh or dry, they certainly serve admirably in enabling Pelopæus to rear brood after brood, and to people the different parts of the earth with abundant representatives of her kind.

WORKERS IN CLAY

THE nests of Pelopæus cœruleus and Pelopæus cementarius, our two mud-daubers, are common under eaves and in other sheltered places, and many a country boy on opening them has been astonished to find that they do not contain wasps, but are crammed with spiders. Let them alone, however, and the wasps will arrive, for somewhere in the mass is an egg; and when it hatches the spiders will serve as breakfast, dinner and tea for the larva, until the change from the Arachnida to the Hymenoptera has been accomplished. Poor spiders! it is a wonder that there are any left, such thousands and tens of thousands are destroyed by these tremendously energetic enemies.

Of what is Pelopæus thinking as, humming loudly, she jams her paralyzed and benumbed victims into her little cylindrical tubes? If only we could get inside of that little head! If only we could be wasps for a day, and then come back and tell about it, how much vain speculation would be saved! We can understand herwhen she soars gayly into the blue, the sunshine flashing from her brilliant wings; we too have felt the delight of health and freedom. She is still comprehensible when, at the close of day, she and her sisters quarrel for the favorite sleeping-places among the carvings of the porch pillars; but we cannot follow her mental processes when, at the moment of building, she surrenders herself to the mysterious sway of instinct, doing she knows not what, but doing it joyously, and preserving through it all the precious possession of her own individuality. Every aspect speaks of pleasure as these wasps gather at well or spring, and, singing contentedly, stand on their heads to gather their loads of mud. Briskly and gayly they fly back and forth, pausing at the nest long enough to pat the soft building material into shape. A single load makes half a ring at the larger part of the nest or a whole one at the bottom; and since one dries before the next is put on, the contour of each ring is visible when the tube is done, giving a very artistic effect. This is only accident, however; the wasp cares nothing about the beauty of the structure, for her next step is to daub the whole with lumps of mud, the walls being thus thickened and strengthened. About forty loads are necessary for each cell, and to build and provision one is a good day’s work.

It is strange enough that with no one to teach her Pelopæus knew how to make her cell; but now she must do her hunting, and it is stranger still that she should be impelled to catch nothing but spiders. How does she know a spider from a fly, and why should she prefer one to the other? Not so unreasonable as some wasps, however, she demands nothing further than that her prey shall belong to this great group, and passes lightly over differences of species and genera. Her powerful sting fits her to cope with anything she may meet; but as the size of the cell must be taken into consideration, and the victim must be carried home on the wing, she is on the lookout for something not too large. Here then she ceases to be an automaton, and to some extent makes use of her wits.

How does Pelopæus seize her spider? When and how many times is it stung? Is the wound given with discrimination, a certain point in the ganglion being pricked, so that the spider may be paralyzed, but not killed? Is there any malaxation?

These were important questions to us, and we were therefore greatly excited over our first hunt. One of the blue wasps came flying along, alighted on our cottage wall, and began her search, creeping into corners and cracks and investigating cottony lumps of web.In a few moments a small Epeira strix (the only species to be found on the cottage) was dislodged, and at once dropped to the floor of the porch. The wasp paid no further attention to it, but went on with her search. Three more spiders, one after the other, were disturbed and dropped to the floor without being followed. The fifth one discovered was a little larger than the others, and was seized by the jaws and first legs of the wasp before it had time to escape. It was then rolled into a ball, or at least so it appeared, and stung, then rolled a little more and stung again, and then carried off. We had scarcely drawn breath after this performance when a second wasp appeared. This one dislodged two spiders, and then caught a third, which was seized and stung without any rolling, and then instantly borne away. A third wasp seized the first spider that she found, and started on her flight at the same moment, stinging it on the wing.

So the game went on, while we waxed warm with the excitement and fascination of the chase. As the hours went by some of the yellow mud-daubers appeared, adding to the interest of the scene, although we could not see that their method differed in the least from that of cœruleus.

Rarely did they succeed in catching a spider untilthey had dislodged two or three. Sometimes the spiders were followed as they dropped, and were caught on the floor, but oftener the wasp let them escape and continued her search on the wall. At the moment of capture we could see that she bent her abdomen under and inflicted a sting, but although we concentrated our attention on the point we could not be sure as to just what part was touched. It is our impression that this first sting was given anywhere, at random, with the object of producing a condition of temporary quiet in the victim, so that the next part of the operation could be carried on with deliberation.

The second step in the procedure was commonly for the wasp to alight upon some neighboring object, usually the branch of a bush or tree, and sting the spider a second time, being evidently in no haste; but the difficulty of following her as she flew, and her habit of alighting above our range of vision, made it almost impossible to see just what she did. She certainly remained on the branch for some moments, either resting quietly or rolling the spider around and around, and had every opportunity to sting it as carefully as she wished; but we afterward found that she followed no exact method, since two thirds of the spiders were killed at the moment of capture, and most of the othersdied within a week, while a few lived for thirty-five or forty days. In this study we opened five hundred and seventy-three cells and handled over two thousand spiders, watching over them from day to day with a magnifying glass, that no sign of life might be neglected.

When Pelopæus has filled her cell, she seals it up and makes another close to it, clusters of from six to twenty being found in one spot. Any especially desirable place is used by great numbers; and they make a lively scene, working eagerly at their nests, dashing off for more mud or bringing in their victims. All animated by the same compelling instinct, they are still individuals, and the character of each enters into her work. One picks up the first spider she sees, no matter how tiny it may be, and makes twenty-five or thirty journeys before her cell is filled, while another seems to have a calculating turn of mind, using four or five big spiders instead of a quantity of small ones. Has she made a note of the calibre of her cell, and determined to save herself trouble by looking farther and selecting the largest ones that will go in?ill271

HORIZONTAL CELLS OF THE MUD-DAUBER

Most of them place their cells vertically; but a few prefer the horizontal position, while still others, undecided as to the matter of direction, make clusters in which some are horizontal and others upright. Occasionallythere is a remarkable innovation in building-material, as where in a group of fifteen, four cells in the centre were constructed of pure white plaster, forming a striking contrast to the surrounding mud color. One wasp built an entire cluster after an original fashion, following the beaten track until the cell was completed, and even bringing mud enough to daub it over, as her sisters were doing, but sticking it all in one spot, so that when the group was complete irregular lumps were attached here and there, leaving visible the elegant architecture of the individual cells. Did she think they were too pretty to spoil? or was she merely one of those radical spirits that rebel against conventionality and demand change for the sake of change? It is these variations that furnish Natural Selection with its materials; but rigid as may be the rules regarding the non-survival of the unfit, we find that the race of Pelopæus still produces many absent-minded wasps, that after spending hours in carefully constructing their nests, seal them up empty, forgetting to put in the spiders or to lay the egg.

When a cell is sealed, the mother wasp ceases to take an interest in it, but she has done all that is necessary. In two or three days the egg hatches, after which the larva spends ten or fifteen days in eating, and then spins its cocoon. Here it remains, perhaps for only a few weeks,—for there are two or three generations in one season,—or perhaps through the long months of winter.

Fabre gives a most entertaining account of a French species of Pelopæus which nests in the wide-mouthed chimneys of the peasant. Undisturbed by the steam of washing day or the bustle of dinner-getting, the wasp enters the open door, passes unconcerned among the human inhabitants, and makes her cells against the smoky bricks, out of reach of the flames. This species kills her prey at the moment of capture, by which act she falls in the estimation of Fabre, who respects a wasp in proportion to the nicety with which she delivers her sting. He says, however, that at least she follows a logical method in turning to account these spiders, menaced with early decay. In the first place the prey is multiplied in each cell. The piece actually attacked by the larva is soon a disorganized mass, likely to decay speedily; but it is small and is consumed before decomposition can advance, for when a larva once attacks aspider it does not leave it for another. The others then remain intact, which is enough to keep them fresh during the short period of larval life. When, on the contrary, the prey consists of a single large piece, it is necessary that the organic life should be maintained, and a special art must also be observed in eating it. It is well then that Pelopæus is inspired to take numerous small pieces. The egg, moreover, is always placed on the first spider brought in, whether the storing of the nest is completed within a few hours, or whether, as in some cases, it occupies several days; and this M. Fabre considers a very happy arrangement.

The French Pelopæi differ from ours at nearly every point. Ours kill only about two thirds of their victims, many of the others being paralyzed so perfectly that they live for two or three weeks. Again, ours, instead of placing the egg upon the first spider, almost invariably lay it upon the last one brought in. Another point of difference is that our larvæ frequently start in by eating up the soft abdomens, like children who first devour the plums in their pudding, returning later to the tough parts that are left, a rash and reprehensible course of action of which their better-taught French cousins are never guilty. When one comes to compare the two sets of facts furnished by the two groups of species, thedeductions which Fabre has drawn as to the importance of the instincts of the French group are seen to be unfounded. The American species violate nearly every principle which he considers necessary to their existence, and yet they flourish and multiply. For our part we find nothing in the actions of Pelopæus that needs to be explained—nothing that is not well adapted to the conditions under which each species works. The measure of praise or blame which we mete out to these depredators is merely a way of saying whether we would or would not follow their methods in provisioning our houses and rearing our children. Perhaps we would always use large spiders and would always have them fresh; but it is evident that tastes differ, and the matter is so purely a subjective affair that it will have to go unsettled. In any event, whether her victims be strong or feeble, old or young, big or little, fresh or dry, they certainly serve admirably in enabling Pelopæus to rear brood after brood, and to people the different parts of the earth with abundant representatives of her kind.

Chapter XIISENSE OF DIRECTIONWE once made a number of experiments to discover in what way the social wasps came back to the nest on returning from their hunting expeditions. Were they endowed with some innate power which made memory of places unnecessary, and enabled them to fly in a straight line to any point they wished to reach, or did their return depend upon the more commonplace method of remembering the appearance of the country-side?One morning at half past eight, we placed a wasp cage over the opening of a yellow-jacket hole that had been closed since the night before, and caught fifty-five workers, after which the nest was again closed, one of us taking the cage out on to the lake, while the other remained to watch for their return.At seven minutes before nine, twenty of the wasps were liberated an eighth of a mile from shore near the end of the island. All, without exception, flew towardthe island and away from the nest. Whether they settled could not be determined. The boat was then moved an eighth of a mile beyond the island to the north, where, at ten minutes after nine, the remaining wasps were set free. They seemed a good deal confused, and flew in all directions. Many returned to the boat and alighted, but soon flew away again. Two that settled on the boat were knocked into the water; but they instantly rose and circled up into the air until out of sight.Of the fifty-five wasps that we set free, thirty-nine returned to the nest by ten o’clock, five of them belonging to the lot that flew to the island, since they soon found their bearings and came directly home, reaching the nest before the wasps of the second lot were liberated.Of the thirty-five wasps that were set free at the second point, at least twenty started in wrong directions. Adding these to the first twenty, we have left only fifteen that appeared to know where to look for their home, and yet thirty-nine reached the nest in a little more than an hour from the time the first wasps were set free.On another morning we caught thirty-eight workers and took them to a boat-house on the shore of the lake, in the second story of which was a large room with twogood-sized windows; one looked west over the lake and away from the nest, the other east toward the nest, and both were wide open. The west window was the brighter, but the other was light, the sun being on that side of the house.We placed the cage in the middle of this room and opened the door, stationing ourselves well to one side so as not to interfere with the movements of the wasps. They came out very naturally, pausing a moment before flying, and followed each other so slowly that we could easily see which window they went out by. Twenty-two flew through the west window away from the nest, and sixteen through the east toward the nest.At another time we took fourteen wasps from the nest of a different species and carried them seventy-three yards to the southeast. The cage was opened so that they could fly out in any direction they chose, and they all started in a straight line for the nest. Later on the same day, we took forty-five from this nest, and set them free one hundred and seventy-six yards to the south. Seven flew north toward the nest, twenty-one south, eight west, and seven east, while the other two circled around as they rose higher and higher, until they were lost to view. None in this experiment returned to take a fresh start.Again, we took twenty-three wasps three hundred yards southeast of the nest and liberated them in an open field; thirteen flew east or south away from the nest, seven west or northwest toward the nest, and four returned to the starting-place and seemed unwilling to venture out again.These observations show that the two species of wasps with which we experimented have no sense of direction in the form of a mysterious additional sense, nor yet in the form of a power by which they keep a register of the turns and changes in a journey and are thus able to retrace their way. Our cage was of wire, and so open that they could see all about, as we carried them from place to place; yet when they flew out, they most frequently started in a wrong direction and toward a point that we had not passed. In many instances, however, these wasps returned to the nest, and it seems highly probable that as they rose higher and higher into the air, circling as they went, they discovered some lofty treetop or other object that had before served them as a landmark, and that in this way they were able to make their way home. Bee-keepers know that if young workers which, in strong hives, pass the first ten or fifteen days of their lives in feeding the larvæ without going abroad, are taken out and set free only a shortdistance from home, they are unable to find their way back, and perish, while those that have passed beyond the nursing stage and have begun to do outside work may be carried long distances away and still readily regain the nest.With the solitary wasps we attacked the problem from the other end. We observed what the social wasps did in attempting to return to the nest; with the solitaries, we watched them when, after making the nest, they prepared to leave it to go out into the fields or woods in search of food or prey, thinking that the procedure of different species under these circumstances would afford a clue to the faculty upon which they depended to find their way about. If they were furnished with an innate sense of direction they would not need to make a study of the locality of the nest in order to find the way back, but if they were without this sense it would be only common prudence to take a good account of their bearings before going far afield.The sight of a bee or a wasp returning to its home from some far distant spot, without hesitation or uncertainty, is indeed marvelous. When we saw our first Ammophila perform this feat we were filled with wonder. How was it possible for her to hunt for hours, in all directions, far and wide, and then return in a directline to a nest which had been so carefully covered over that every trace of its existence was obliterated?To say that she is a creature of instinct, however, is not quite fair to her ladyship’s intelligence, as a better acquaintance with her would prove. In reading much popular natural history one might suppose that the insects seen flying about on a summer’s day were a part of some great throng which is ever moving onward, those that are here to-day being replaced by a new set on the morrow. Except during certain seasons the exact opposite of this is true. The flying things about us abide in the same locality and are the inhabitants of a fairly restricted area. The garden in which we worked was, to a large extent, the home of a limited number of certain species of wasps that had resided there from birth, or having found the place accidentally, had settled there permanently. To make this matter clear let us suppose the case of an individual of A. urnaria. In June she spent her time in sipping nectar from the onion flowers or from the sorrel that grew on the border of the garden. In July came the days of her courtship and honeymoon, and these too were passed in going from flower to flower, from one part of the garden to another. Many a day we have followed her when she flew from blossom to blossom along a row of bean plants, turning, whenshe reached the end, and wending her way leisurely back along the next row. Then comes a day when we see her running over the ground and looking carefully under the weeds for a good nesting-place. At last a spot is selected and she begins to dig; but two or three times before the work is completed she goes away for a short flight. When it is done, and covered over, she flies away, but returns again and again within the next few hours, to look at the spot and, perhaps, to make some little alteration in her arrangements. From this time on, until the caterpillars are stored and the egg laid, she visits her nest several times a day, so that she becomes perfectly familiar with the neighborhood, and it is not surprising, after all, that she is able to carry her prey from any point in her territory in a nearly direct line to her hole—we say nearly direct, for there was almost invariably some slight mistake in the direction which made a little looking about necessary before the exact spot was found.After days passed in flying about the garden—going up Bean Street and down Onion Avenue, time and time again—one would think that any formal study of the precise locality of a nest might be omitted; but it was not so with our wasps. They made repeated and detailed studies of the surroundings of their nests.Moreover, when their prey was laid down for a moment on the way home, they felt the necessity of noting the place carefully before leaving it.Of the species that catch their prey before making the nest we have good examples in Pompilus quinquenotatus, the tornado wasp, and fuscipennis, the Pompilus with the red girdle.ill283COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN FINDING HER SPIDER AND IN RETRACING HER STEPS TO THE NEST[5]The tornado wasp may make her nest anywhere from one to ten feet from the spot on which she has deposited her spider, while fuscipennis never goes more than fourteen inches away. During the process of excavation both of these wasps pay several visits to the spider, and frequently they have difficulty in finding it. As an example of this kind of trouble we give a diagram of the course followed by an individual of fuscipennis after she had finished her nest, in trying to find her spider and in bringing it home. This and the other similar diagrams that are given are reductions of large tracings that were made on the spot. Although not absolutely correct they are exact enough for all practical purposes, since wherever there is an error it is necessarily in the direction of making the path pursued by the wasp appear shorter and less complex than it really was. The individual in question had placed her spider on a cucumber vine which lay on the ground, not hidden by leaves, but fully exposed to view. The nest was only eight inches away, but when it was finished and the wasp went to bring the spider, she found it only after a search of three minutes; and then when she wentback to the nest she at first passed to one side and went some inches beyond, so that she had to retrace her steps.Marchal notes that some wasps are very unskillful in finding their way about, showing by their errors and hesitations not only that they have no sense of direction, but that they are badly served by their memory and by what senses they have. He draws this conclusion from his own observations, one of which had for its subject Pompilus seriaceus, which nests, conveniently for him, in the walls of the rustic summer-house which he uses for a laboratory. A wasp of this species, having caught her spider, had a most wearisome experience in getting it to the nest, which had been previously excavated near the ground. She first carried it straight up, not only passing the opening, but going to the very top of the wall. Realizing that she had gone wrong, she laid it down, and after a prolonged hunt up and down, to the right and to the left, found the nest; but on leaving it again to go for the spider, she started in exactly the wrong direction, down instead of up; and not until forty minutes had been spent in searching alternately for spider and for nest did she finally bring the two together.The best evidence that wasps depend upon a knowledgeof the place in returning to their nests is given by the pains they take to acquire that knowledge. When Sphex ichneumonea was ready to dig her nest, she had great difficulty in finding a place that suited her. Many a spot was merely looked at and passed by, while others that seemed more attractive were left after they had been excavated for a little way. At last, the nest dug, she was ready to go out and seek for her store of provisions; and now came a most thorough and systematic study of the surroundings. The nests that had been partly made and then deserted had been left without any circling. Evidently she was conscious of the difference and meant, now, to take all necessary precautions against losing her way. She flew in and out among the plants, first in narrow circles near the surface of the ground, and now in wider and wider ones as she rose higher in the air, until at last she took a straight line and disappeared in the distance. Very often, after one thorough study of the topography of her home has been made, a wasp goes away a second time with much less circling or with none at all.If the examination of the objects about the nest makes no impression upon the wasp, or if it is not remembered, she ought not to be inconvenienced nor thrown off her track when weeds and stones are removedand the surface of the ground is smoothed over; but this is just what happens. Aporus fasciatus entirely lost her way when we broke off the leaf that covered her nest, but found it, without trouble, when the missing object was replaced. All of the species of Cerceris were extremely annoyed if we placed any new object near their nesting-places. One Ammophila refused to make use of her burrow after we had drawn some deep lines in the dust before it. The same annoyance is exhibited when there is any change made near the spot upon which the prey of the wasp, whatever it may be, is deposited temporarily. We learned from experience how important it was not to disarrange the grass or plants on such occasions. The wasps are in many cases so prudent as to conceal their booty among the leaves; and this made it very inconvenient to keep our eyes upon the captured prey, as was quite necessary if we wished to follow it on its travels. To avoid the discomfort of lying on the ground or of twisting the neck at some impossible angle for half an hour at a time, we sometimes gently moved the intercepting objects to one side; but even such a slight change cost us dear in time and patience, as it threw the wasp out of her bearings and made it difficult for her to recover her treasure. We recall one exceedingly warm day in September when we weredelayed in this way for forty minutes, when she would have seized the spider and gone on her way without a pause had we not interfered.ill288LOCALITY STUDY OF ASTATA BICOLOR[6]Very often the wind would shake the plant so that the spider or caterpillar would fall to the ground. Under these circumstances the wasp was not at all disconcerted, but, on not finding her prey where she had left it, dropped at once to where it was lying. This is probably only an extension of their ordinary habits. A wasp that takes spiders learns to follow them as they drop from the web on being disturbed. In this they are evidently guided by sight, but perhaps they are also aided by the sense of smell under other conditions,—to the extent, at least, of recognizing the place upon which their prey has lain. With so much to build upon, it is easy to see how natural selection may have perfected the habit. We are delaying a long time over details, but we feel that to invoke an unknown sense is permissible only after a careful study of the daily life of the animals in question has left the problem unsolved.ill289LOCALITY STUDY OF ASTATA UNICOLOR[7]Among the wasps that first make the nest and then provision the larder, Astata bicolor is one of the most interesting. She makes a permanent abiding-place, and probably uses it until all of her eggs are laid. It is evident that since she comes and goes many times during the several weeks of her occupation, she does not need to make a prolonged study of the environment at every departure. Her first survey, just after the nest is completed, is most thorough; and, as a usual thing, when she first comes out on each succeeding morning, she reviews the situation more or less carefully. Individuals differ in this respect, however, some studying their local habitat much more than others. In this as well as in all other matters our observations are in complete accord with those of Sir John Lubbock, who says: “Indeed, many of my experiences seem to show not only a difference of character in the different species of ants, but that even within the limits of the same speciesthere are individual differences between ants, just as between men.”[8]This little bug-hunting Astata bicolor made her study in a different way from Sphex ichneumonea. She first flew from the nest to a spot near by and settled there, returning, after a moment, to the nest, or else flying to another resting-place. After pausing in a number of places (in the case of the one followed in the diagram, thirteen), she finished by a rapid zigzag flight. Another wasp of this genus, unicolor, differed from bicolor in not returning to the nest from the different resting-places, and inwalking from one to another of them instead of flying, although the last part of the study was made on the wing.ill290SECOND LOCALITY STUDY OF A. UNICOLOR[9]Cerceris deserta was one of the wasps that objected strongly to our presence, and she also made a great deal of fuss about leaving her nest. Nearly all the species circle before leaving a spot to which they intend to return, but deserta begins her flight with a series of short zigzags in the form of a half circle on one side of the nest. C. nigrescens, too, begins with semicircles, while C. clypeata flies entirely around and around theopening. The contrast between the deliberate movements of Astata and the rapid flight of Cerceris is very striking.We have now given a sufficient number of instances, from widely separated genera, to show the care that is taken by wasps to acquaint themselves with the surroundings of their nests. It has also been shown that in spite of all this care they frequently have trouble in finding their way about. All these facts have led us to conclude that wasps are guided in their movements by their memory of localities. They go from place to place quite readily because they are familiar with the details of the landscape in the district they inhabit. Fair eyesight and a moderately good memory on their part are all that need be assumed in this simple explanation of the problem.

SENSE OF DIRECTION

WE once made a number of experiments to discover in what way the social wasps came back to the nest on returning from their hunting expeditions. Were they endowed with some innate power which made memory of places unnecessary, and enabled them to fly in a straight line to any point they wished to reach, or did their return depend upon the more commonplace method of remembering the appearance of the country-side?

One morning at half past eight, we placed a wasp cage over the opening of a yellow-jacket hole that had been closed since the night before, and caught fifty-five workers, after which the nest was again closed, one of us taking the cage out on to the lake, while the other remained to watch for their return.

At seven minutes before nine, twenty of the wasps were liberated an eighth of a mile from shore near the end of the island. All, without exception, flew towardthe island and away from the nest. Whether they settled could not be determined. The boat was then moved an eighth of a mile beyond the island to the north, where, at ten minutes after nine, the remaining wasps were set free. They seemed a good deal confused, and flew in all directions. Many returned to the boat and alighted, but soon flew away again. Two that settled on the boat were knocked into the water; but they instantly rose and circled up into the air until out of sight.

Of the fifty-five wasps that we set free, thirty-nine returned to the nest by ten o’clock, five of them belonging to the lot that flew to the island, since they soon found their bearings and came directly home, reaching the nest before the wasps of the second lot were liberated.

Of the thirty-five wasps that were set free at the second point, at least twenty started in wrong directions. Adding these to the first twenty, we have left only fifteen that appeared to know where to look for their home, and yet thirty-nine reached the nest in a little more than an hour from the time the first wasps were set free.

On another morning we caught thirty-eight workers and took them to a boat-house on the shore of the lake, in the second story of which was a large room with twogood-sized windows; one looked west over the lake and away from the nest, the other east toward the nest, and both were wide open. The west window was the brighter, but the other was light, the sun being on that side of the house.

We placed the cage in the middle of this room and opened the door, stationing ourselves well to one side so as not to interfere with the movements of the wasps. They came out very naturally, pausing a moment before flying, and followed each other so slowly that we could easily see which window they went out by. Twenty-two flew through the west window away from the nest, and sixteen through the east toward the nest.

At another time we took fourteen wasps from the nest of a different species and carried them seventy-three yards to the southeast. The cage was opened so that they could fly out in any direction they chose, and they all started in a straight line for the nest. Later on the same day, we took forty-five from this nest, and set them free one hundred and seventy-six yards to the south. Seven flew north toward the nest, twenty-one south, eight west, and seven east, while the other two circled around as they rose higher and higher, until they were lost to view. None in this experiment returned to take a fresh start.

Again, we took twenty-three wasps three hundred yards southeast of the nest and liberated them in an open field; thirteen flew east or south away from the nest, seven west or northwest toward the nest, and four returned to the starting-place and seemed unwilling to venture out again.

These observations show that the two species of wasps with which we experimented have no sense of direction in the form of a mysterious additional sense, nor yet in the form of a power by which they keep a register of the turns and changes in a journey and are thus able to retrace their way. Our cage was of wire, and so open that they could see all about, as we carried them from place to place; yet when they flew out, they most frequently started in a wrong direction and toward a point that we had not passed. In many instances, however, these wasps returned to the nest, and it seems highly probable that as they rose higher and higher into the air, circling as they went, they discovered some lofty treetop or other object that had before served them as a landmark, and that in this way they were able to make their way home. Bee-keepers know that if young workers which, in strong hives, pass the first ten or fifteen days of their lives in feeding the larvæ without going abroad, are taken out and set free only a shortdistance from home, they are unable to find their way back, and perish, while those that have passed beyond the nursing stage and have begun to do outside work may be carried long distances away and still readily regain the nest.

With the solitary wasps we attacked the problem from the other end. We observed what the social wasps did in attempting to return to the nest; with the solitaries, we watched them when, after making the nest, they prepared to leave it to go out into the fields or woods in search of food or prey, thinking that the procedure of different species under these circumstances would afford a clue to the faculty upon which they depended to find their way about. If they were furnished with an innate sense of direction they would not need to make a study of the locality of the nest in order to find the way back, but if they were without this sense it would be only common prudence to take a good account of their bearings before going far afield.

The sight of a bee or a wasp returning to its home from some far distant spot, without hesitation or uncertainty, is indeed marvelous. When we saw our first Ammophila perform this feat we were filled with wonder. How was it possible for her to hunt for hours, in all directions, far and wide, and then return in a directline to a nest which had been so carefully covered over that every trace of its existence was obliterated?

To say that she is a creature of instinct, however, is not quite fair to her ladyship’s intelligence, as a better acquaintance with her would prove. In reading much popular natural history one might suppose that the insects seen flying about on a summer’s day were a part of some great throng which is ever moving onward, those that are here to-day being replaced by a new set on the morrow. Except during certain seasons the exact opposite of this is true. The flying things about us abide in the same locality and are the inhabitants of a fairly restricted area. The garden in which we worked was, to a large extent, the home of a limited number of certain species of wasps that had resided there from birth, or having found the place accidentally, had settled there permanently. To make this matter clear let us suppose the case of an individual of A. urnaria. In June she spent her time in sipping nectar from the onion flowers or from the sorrel that grew on the border of the garden. In July came the days of her courtship and honeymoon, and these too were passed in going from flower to flower, from one part of the garden to another. Many a day we have followed her when she flew from blossom to blossom along a row of bean plants, turning, whenshe reached the end, and wending her way leisurely back along the next row. Then comes a day when we see her running over the ground and looking carefully under the weeds for a good nesting-place. At last a spot is selected and she begins to dig; but two or three times before the work is completed she goes away for a short flight. When it is done, and covered over, she flies away, but returns again and again within the next few hours, to look at the spot and, perhaps, to make some little alteration in her arrangements. From this time on, until the caterpillars are stored and the egg laid, she visits her nest several times a day, so that she becomes perfectly familiar with the neighborhood, and it is not surprising, after all, that she is able to carry her prey from any point in her territory in a nearly direct line to her hole—we say nearly direct, for there was almost invariably some slight mistake in the direction which made a little looking about necessary before the exact spot was found.

After days passed in flying about the garden—going up Bean Street and down Onion Avenue, time and time again—one would think that any formal study of the precise locality of a nest might be omitted; but it was not so with our wasps. They made repeated and detailed studies of the surroundings of their nests.Moreover, when their prey was laid down for a moment on the way home, they felt the necessity of noting the place carefully before leaving it.

Of the species that catch their prey before making the nest we have good examples in Pompilus quinquenotatus, the tornado wasp, and fuscipennis, the Pompilus with the red girdle.

ill283

COURSE FOLLOWED BY POMPILUS FUSCIPENNIS IN FINDING HER SPIDER AND IN RETRACING HER STEPS TO THE NEST[5]

The tornado wasp may make her nest anywhere from one to ten feet from the spot on which she has deposited her spider, while fuscipennis never goes more than fourteen inches away. During the process of excavation both of these wasps pay several visits to the spider, and frequently they have difficulty in finding it. As an example of this kind of trouble we give a diagram of the course followed by an individual of fuscipennis after she had finished her nest, in trying to find her spider and in bringing it home. This and the other similar diagrams that are given are reductions of large tracings that were made on the spot. Although not absolutely correct they are exact enough for all practical purposes, since wherever there is an error it is necessarily in the direction of making the path pursued by the wasp appear shorter and less complex than it really was. The individual in question had placed her spider on a cucumber vine which lay on the ground, not hidden by leaves, but fully exposed to view. The nest was only eight inches away, but when it was finished and the wasp went to bring the spider, she found it only after a search of three minutes; and then when she wentback to the nest she at first passed to one side and went some inches beyond, so that she had to retrace her steps.

Marchal notes that some wasps are very unskillful in finding their way about, showing by their errors and hesitations not only that they have no sense of direction, but that they are badly served by their memory and by what senses they have. He draws this conclusion from his own observations, one of which had for its subject Pompilus seriaceus, which nests, conveniently for him, in the walls of the rustic summer-house which he uses for a laboratory. A wasp of this species, having caught her spider, had a most wearisome experience in getting it to the nest, which had been previously excavated near the ground. She first carried it straight up, not only passing the opening, but going to the very top of the wall. Realizing that she had gone wrong, she laid it down, and after a prolonged hunt up and down, to the right and to the left, found the nest; but on leaving it again to go for the spider, she started in exactly the wrong direction, down instead of up; and not until forty minutes had been spent in searching alternately for spider and for nest did she finally bring the two together.

The best evidence that wasps depend upon a knowledgeof the place in returning to their nests is given by the pains they take to acquire that knowledge. When Sphex ichneumonea was ready to dig her nest, she had great difficulty in finding a place that suited her. Many a spot was merely looked at and passed by, while others that seemed more attractive were left after they had been excavated for a little way. At last, the nest dug, she was ready to go out and seek for her store of provisions; and now came a most thorough and systematic study of the surroundings. The nests that had been partly made and then deserted had been left without any circling. Evidently she was conscious of the difference and meant, now, to take all necessary precautions against losing her way. She flew in and out among the plants, first in narrow circles near the surface of the ground, and now in wider and wider ones as she rose higher in the air, until at last she took a straight line and disappeared in the distance. Very often, after one thorough study of the topography of her home has been made, a wasp goes away a second time with much less circling or with none at all.

If the examination of the objects about the nest makes no impression upon the wasp, or if it is not remembered, she ought not to be inconvenienced nor thrown off her track when weeds and stones are removedand the surface of the ground is smoothed over; but this is just what happens. Aporus fasciatus entirely lost her way when we broke off the leaf that covered her nest, but found it, without trouble, when the missing object was replaced. All of the species of Cerceris were extremely annoyed if we placed any new object near their nesting-places. One Ammophila refused to make use of her burrow after we had drawn some deep lines in the dust before it. The same annoyance is exhibited when there is any change made near the spot upon which the prey of the wasp, whatever it may be, is deposited temporarily. We learned from experience how important it was not to disarrange the grass or plants on such occasions. The wasps are in many cases so prudent as to conceal their booty among the leaves; and this made it very inconvenient to keep our eyes upon the captured prey, as was quite necessary if we wished to follow it on its travels. To avoid the discomfort of lying on the ground or of twisting the neck at some impossible angle for half an hour at a time, we sometimes gently moved the intercepting objects to one side; but even such a slight change cost us dear in time and patience, as it threw the wasp out of her bearings and made it difficult for her to recover her treasure. We recall one exceedingly warm day in September when we weredelayed in this way for forty minutes, when she would have seized the spider and gone on her way without a pause had we not interfered.ill288

LOCALITY STUDY OF ASTATA BICOLOR[6]

Very often the wind would shake the plant so that the spider or caterpillar would fall to the ground. Under these circumstances the wasp was not at all disconcerted, but, on not finding her prey where she had left it, dropped at once to where it was lying. This is probably only an extension of their ordinary habits. A wasp that takes spiders learns to follow them as they drop from the web on being disturbed. In this they are evidently guided by sight, but perhaps they are also aided by the sense of smell under other conditions,—to the extent, at least, of recognizing the place upon which their prey has lain. With so much to build upon, it is easy to see how natural selection may have perfected the habit. We are delaying a long time over details, but we feel that to invoke an unknown sense is permissible only after a careful study of the daily life of the animals in question has left the problem unsolved.ill289

LOCALITY STUDY OF ASTATA UNICOLOR[7]

Among the wasps that first make the nest and then provision the larder, Astata bicolor is one of the most interesting. She makes a permanent abiding-place, and probably uses it until all of her eggs are laid. It is evident that since she comes and goes many times during the several weeks of her occupation, she does not need to make a prolonged study of the environment at every departure. Her first survey, just after the nest is completed, is most thorough; and, as a usual thing, when she first comes out on each succeeding morning, she reviews the situation more or less carefully. Individuals differ in this respect, however, some studying their local habitat much more than others. In this as well as in all other matters our observations are in complete accord with those of Sir John Lubbock, who says: “Indeed, many of my experiences seem to show not only a difference of character in the different species of ants, but that even within the limits of the same speciesthere are individual differences between ants, just as between men.”[8]

This little bug-hunting Astata bicolor made her study in a different way from Sphex ichneumonea. She first flew from the nest to a spot near by and settled there, returning, after a moment, to the nest, or else flying to another resting-place. After pausing in a number of places (in the case of the one followed in the diagram, thirteen), she finished by a rapid zigzag flight. Another wasp of this genus, unicolor, differed from bicolor in not returning to the nest from the different resting-places, and inwalking from one to another of them instead of flying, although the last part of the study was made on the wing.

ill290

SECOND LOCALITY STUDY OF A. UNICOLOR[9]

Cerceris deserta was one of the wasps that objected strongly to our presence, and she also made a great deal of fuss about leaving her nest. Nearly all the species circle before leaving a spot to which they intend to return, but deserta begins her flight with a series of short zigzags in the form of a half circle on one side of the nest. C. nigrescens, too, begins with semicircles, while C. clypeata flies entirely around and around theopening. The contrast between the deliberate movements of Astata and the rapid flight of Cerceris is very striking.

We have now given a sufficient number of instances, from widely separated genera, to show the care that is taken by wasps to acquaint themselves with the surroundings of their nests. It has also been shown that in spite of all this care they frequently have trouble in finding their way about. All these facts have led us to conclude that wasps are guided in their movements by their memory of localities. They go from place to place quite readily because they are familiar with the details of the landscape in the district they inhabit. Fair eyesight and a moderately good memory on their part are all that need be assumed in this simple explanation of the problem.

Back to Index Next