Wasps, Social and Solitary

by George W. Peckham; E. G. Peckham

At eleven o’clock on the morning of a warm day in mid-August we saw the steel-blue Pompilus scelestus dragging a big Lycosid across a field. The spider was sixteen millimeters long and wide in proportion, while the wasp was but thirteen millimeters long and very slender, so that the weight of the spider was at least three times that of its captor. The necessity for going backward was evident in this case, but the wasp moved rapidly considering the load that she was dragging. As she worked her way along she made frequent pauses, stopping for two or three minutes at a time in some little hollow, or under leaves or weeds. She spent a good deal of time, during these pauses, in cleaning herself, and a good deal of time also in doing something to the spider which we could not understand. She seemed to be biting the legs, near the body, beginning with an anterior leg on one side and working backward, and then repeating the operation on the other side. She went through this squeezing process again and again, and to us it looked as though she might be trying to force back the juices from the legs into the body preparatory to cutting them off; but after a time she would seize her prey and start on again. She had made her way along in this fashion for some ten feet, when a second wasp appeared and alighted on a weed near by. This interloper was a trifle smaller than the other, and from her actions was evidently greatly interested in the paralyzed spider. When the Pompilus stopped for a moment the other moved from stem to stem in a stealthy manner just as a cat stalks a bird. The rightful owner of the prey was disturbed and dashed at her, driving her away again and again, but she flew only a short distance and was soon back, always creeping nearer and nearer to the spider. We, too, were watching with closest attention, but our desire was to see the speedy homecoming of Pompilus and to learn whether she cut off the legs of her victim; and so, interesting as was the contest between the wasp and the wasp-inquiline, we decided to interfere and remove the intruder. This was very easily accomplished, since the little insect was so intent upon following the spider that she was oblivious to our presence, and allowed us to place a bottle over her as she stood eagerly looking for a chance to advance. Her removal gave great relief to the other wasp, as was manifested by an entire change of manner. Before, she had been constantly on the lookout, moving only with the greatest circumspection, but now she relaxed her vigilance. With the Ceropales in our vial we, too, felt relieved, and now the path of discovery seemed clear before us; but scarcely had things assumed their old status when a second enemy, a much larger and bolder Ceropales, threw both the Pompilus and ourselves into consternation. Again we took the side of our wasp and drove the other one off, but only to see it return a few moments later. The Pompilus now flew at it in a most gallant fashion and pursued it far afield, but when she came back the enemy was but a few seconds behind her. Here we again interposed and removed the second Ceropales from the field of action.

All cause for anxiety being over, the wasp now resumed her journey. Before long she came to a shallow depression in the ground which was partly sheltered by an overhanging lump of earth, and under this covering she dropped the spider and again began to squeeze its legs. After a moment she removed it to the other side of the depression, where it was subjected to further manipulation. Next, her toilet was attended to, and then the spider was carried back and placed again under the lump of earth. At least ten times was that limp and helpless creature dragged from one side to the other of the little depression, a distance of about two inches, the time between being filled in by the wasp with cleaning herself and squeezing the legs of her victim. After forty minutes of this tedious delay the moment came when she picked up her burden with renewed determination and started rapidly on her way. We kept very close to her, but she did not allow our presence to interrupt her work, and, indeed, paid no attention to it. After she had gone along for a distance of about eight feet there was another pause, of only five minutes this time, and when she resumed her onward march it was in a new direction. Thus far she had gone almost due south, but now she turned and went six feet toward the west. Suddenly the spider was dropped. There was no hole in sight, but the wasp seemed to feel that some important crisis had arrived. Her whole manner was excited and flurried, and we thought that surely we had reached the neighborhood of the nest. How little we understood her! Her nest was still far away, and it may be that she had just begun to realize that the task she had undertaken was too heavy for her accomplishment—that at her present rate of progress her strength would be exhausted before she could reach her goal. At any rate, something was wrong. The spider was left unprotected on the ground while she made a number of long excursions without it, sometimes being gone as much as fifteen minutes. On coming back from these trips she would return to the task of squeezing the legs with such energy and persistence that we expected to see them drop off. Then she would run over the ground in all directions, looking under lumps of earth and stones and poking her head into every little hole. Was she trying to find some suitable spot near at hand to take the place of the one which she had prepared or selected at a distance?

One hour from the time of her arrival at this place, and two hours from the time that we began to watch her, she flew away and was gone for an unusually long time. We can only suppose that when she absented herself in this way she was visiting the spot to which she wished to convey her booty. On her return she seemed to be filled with a new idea, for after climbing to the top of a tall stout weed that grew near by, she came down, seized the spider, and tried to drag it up the stem. Perhaps she meant to lift it to such an elevation that she could fly with it, but it was too heavy for her and fell after she had raised it to a height of three inches. She then flew away again, and on her return we caught her, fearing that she was becoming discouraged and that she might presently depart to be seen no more. Had there been any prospect of her solving the difficulty that beset her our patience might have held out to the end, but this was evidently a case in which there was a failure of instinct, or intelligence, or whatever faculty was concerned.

More than a year passed before we had another opportunity of solving this problem of scelestus, and the pleasure with which we hailed her second appearance in our garden may be easily imagined. This time the wasp had made her nest, but was not ready to fill it, and when we first saw her she was running about without any particular aim in view, although at the time we supposed her to be hunting. Before long she went and took a look at the neat round hole which she had made near the fence that separates the garden from the woods. The earth that had been taken out either had been carried to a distance or had been swept away after the digging was completed, for there was no pile to be seen. This was at two o’clock of a cloudy afternoon. It may be that she needed the stimulus of sunshine to make her hunt, or perhaps she realized that what was left of the day would not give her sufficient time to capture her spider and bring it home. At any rate, she spent the remainder of the afternoon in making short excursions around her nest, attended, at a little distance, by a smaller blue wasp, Pompilus subviolaceus, whose presence she did not seem to notice. These trips took her from ten to twenty feet from the nest, each occupying from fifteen minutes to half an hour. At every return to the nest she flattened herself out on the ground and wriggled in the dust, and then dragged herself all around it in the strangest manner. Perhaps these actions were indications of pleasurable emotion. We had seen them once before, in Priononyx atrata just before she carried a locust into her nest.

At a little after four o’clock she began to investigate, very carefully, the plants and grasses that immediately surrounded her hole, showing an especial interest in one bunch of clover that grew four inches away. Into this she finally vanished, and peering curiously among the greenery, we discovered her hanging to a leaf, which was sheltered by thick foliage on all sides. Here she remained motionless and probably fast asleep until sundown, when we left her for the night.

When we went to the garden at eight o’clock on the following morning, subviolaceus was on hand, but scelestus was still sound asleep in her leafy bower. We thought it best to awaken her, for a large spider had spread its web just below, and if the wasp should drop upon it nothing could save her. We therefore aroused her gently, whereupon she crept slowly up the stem and, taking her stand on the highest point, surveyed the world. Then, after stretching herself sleepily, she made her toilet, cleaning off her wings and legs, and washing her face with her feet like a cat. When these duties were finished she walked slowly about for an hour, visiting her nest every now and then. Suddenly, at half past nine o’clock, her whole manner changed, and seeming very much excited she ran rapidly along, parallel with the fence, for fifteen or twenty feet, and then, rising on her wings, flew far away into the woods. She had evidently gone hunting at last, and we watched eagerly for her return. She was not successful at once, however, for at half past ten she came back without anything, stayed at the nest for a few minutes, and then flew to the woods again with the same excited manner as before. Perhaps she had already caught her spider at some far distant spot, and was getting her bearings preparatory to bringing it home; but it was half past one when she suddenly appeared, five or six inches from the nest, coming backward through the fence, and dragging a large Lycosid. This she laid down close by, and began to bite at the legs quite after the manner of the wasp we had seen the year before. Her movements were full of nervous excitement, in marked contrast to those of the previous day. Presently she went to look at her nest, and seemed to be struck with a thought that had already occurred to us—that it was decidedly too small to hold the spider. Back she went for another survey of her bulky victim, measured it with her eye, without touching it, drew her conclusions, and at once returned to the nest and began to make it larger. We have several times seen wasps enlarge their holes when a trial had demonstrated that the spider would not go in, but this seemed a remarkably intelligent use of the comparative faculty. Her method of work was peculiar. Standing in the tunnel with her head down and her abdomen curved under, she bit the earth loose with her mandibles and pushed it under her body and beyond the tip of the abdomen. When a little had accumulated she backed out, holding it in this way.

While she was thus employed the spider was attacked by a very tiny red ant, that could not by any possibility have stirred it. When the wasp caught sight of this insignificant marauder she fell into a fit of wild fury, and bending her abdomen under, seized the ant again and again in her mandibles, and flung it backward against the tip of her sting. The little creature finally escaped, seeming none the worse for the rough handling to which it had been subjected, while the wasp, still trembling with excitement, grasped her spider and rushed off to a distance of several feet, carrying it up on a weed and depositing it there. The labor of excavation was then resumed, and after a half-hour’s work the nest was completed to her satisfaction.

Coming up head first, she flattened herself out on the ground, and sprawling thus, dragged herself all around it. The spider was now brought to the nest, being left once on the way while she ran in and out again, and was taken in after a new and original fashion. Backing in herself, she seized it by the tip of the abdomen and dragged it down without any trouble, since the legs were gently pushed up over the head and made no resistance.

In two minutes she emerged from the opening, and standing on the four posterior legs, with her abdomen hanging down into the hole, scratched the earth backward with the front legs and mandibles. As it fell in she pushed it down with the abdomen, and as the hole filled she raised herself higher and higher on her legs, still using the tip of the abdomen to work the material into place.