Wasps, Social and Solitary

by George W. Peckham; E. G. Peckham

POMPILUS MARGINATUS

This was our first specimen of marginatus, and a month passed before we met another. It was while watching some Bembecidæ that we saw the pretty little orange-spotted worker dragging a small Thomisid across their nesting-ground. The spider was so small that she held it in her mandibles well above the ground, and we speak of her as dragging it only because she walked backward and acted as though she were obliged to exert herself. Quite often the spiders taken by this species are too large to be carried, and then it is necessary to drag them; this habit is so ingrained that when it would be much more convenient to go straight ahead they stick to the ancient custom, and seem unable to move in any other way. This little wasp was in a frantic hurry, running backward into the Bembex holes and then scrambling out again, until she had crossed the field and had turned to one side, having gone, since we first saw her, about fifteen feet. Here she dropped the spider and began to skim over the ground—it could not be called running and yet it was not flying—until she found a circular hole in the black earth, which looked as if it ran vertically downward. At the time we thought that this was a nest that she had made for herself, but we afterward concluded that it had been excavated by some other creature, that she had found it and determined to make use of it, and that she was bringing her prey to the spot with that end in view. Without entering she rushed back to the spider, but after carrying it a few inches, dropped it and ran to take another look at the nest. By this time, however, she was too much excited to know what she was about, and for five minutes she scurried over the ground without finding it. During this time she picked up the spider four times, carried it a little way, and then dropped it. The last time she carried it to the edge of the grass and stowed it there, this being her first attempt at concealment. She now found the hole again and brought the spider nearly to it, but by this time she was perfectly beside herself. The spider was seized again and again, only to be dropped the next second, while the wasp rushed back and forth between it and the hole. In time this method of procedure brought it close to the nest, but it was carried around the edge once or twice even then. At last, accidentally as it seemed, it fell in, when the wasp quickly ran in also and pulled it down. For half an hour she remained inside, and when she came out we caught her to make sure of her identity. As we set her free immediately we expected her to go to work at covering her nest, but in this we were disappointed, for she did not return. We left the place undisturbed from the thirteenth to the fifteenth of August, when we dug up the nest. The Thomisid was there, but we could find neither egg nor larva. The spider was alive, as was shown by a quivering of the legs. This quivering grew fainter and fainter, until upon the nineteenth it was scarcely perceptible, and on the twenty-first the spider was dead. Our first spider had been stung to death at once, while this one lived seven days and a half after being stored.

On September first, while out in the bean patch, we saw a large Lycosid running madly, first in one direction and then in another. Hovering eagerly and excitedly just above was our marginatus, dashing down at the spider again and again as it came into view for an instant, and then circling wildly around until it appeared once more. Now she pounced upon the frightened spider but missed her aim, now she really grasped it but was shaken off. At last the end came. The wasp descended upon the doomed spider, and there was a violent struggle, both the combatants rolling over and over upon the ground, while all that we could distinguish was the flashing of the red upon the body of the wasp. In an instant it was over, and the wasp rose, leaving the spider limp and motionless upon its back. In our other examples of marginatus the spider taken had been so small that the wasp might easily have held it and thrust her sting into any spot that she pleased, but this Lycosid was a different antagonist. Where the two were so nearly matched, there could have been but slight opportunity for skillful surgery. In point of strength the wasp was at a disadvantage, and she must have come off victor by the quick use of her sting. Under these circumstances she must have struck when and where she could, without selecting any particular spot. That she quite realized the power of her foe was shown by her next action. With the utmost circumspection she settled down upon the spider and made a prolonged and careful examination of the mouth parts. The investigation was satisfactory, and without any further stinging she seized the spider by one leg, and this time really dragged it off. It was a good load for her, and it evidently required all of her strength to pull it along. Not far away was a lump of earth, under which the treasure was stowed; and then began the usual hunting performance, which soon resulted in the discovery of another cavity which had a very small opening.

She crept in, remained a minute, and then came out and brought her spider to this new hiding-place. The head went in easily, but it took a great deal of tugging to get the rest to follow. At last both spider and wasp were out of sight, and everything remained quiet for so long that we began to think that this time we were really to see the final act in the play. But no; when the little wasp came creeping out it was only to start off on another extended tour, in which we did not attempt to follow her. She doubtless selected another halting-place, for when she returned it was to try to get the spider out of the hole by pulling at one of its hind legs. The task, however, was not an easy one. She exerted all her strength, so that we expected to see the victim torn to pieces before our eyes, and still it did not come. At last she seemed to realize that there was more than one way to accomplish her end, and turned her attention to cutting away the earth to make the opening larger. After a few moments’ work she tried again, and although the passage was still much too small for convenience the spider was at length dragged forth, looking much the worse for wear. As she moved away we alarmed her by lifting some vines that prevented our keeping her in view, and she flew up, leaving the spider on the ground. We seized the opportunity to bend and twist the plants this way and that so that the ground might be left uncovered. The changes that we made probably disconcerted her, for she seemed to lose track of her prey. For over half an hour she hunted about, circling above the place and running around and around over the ground. She often came so close to the spider that we could not understand why she did not see it. At last it was recovered, and again she started off. We tried to follow her, but the vines were so thick that, in spite of our efforts, she soon disappeared into the undiscovered country which we had thus far been unable to penetrate.

Up to this time we had been entirely unable to understand the actions of marginatus, and each new example added to our confusion instead of clearing it away. We were inclined to think that she never made a nest for herself, but caught her spider and then hurried about for a good place to store it, and that her absurd conduct was the result of an indecision of character which made it extremely difficult for her to choose a place and be contented with it. The last part of this judgment holds true, even now when we know her whole history, but we have at last learned that she does dig her own nest.

We had watched a wasp for some time as she carried her spider from place to place, and finally saw her take it into a crevice among some rough lumps of earth which she had previously examined. We expected one of the long spells of eventless waiting to which she had accustomed us, but on lying down and peering into the hole we found that there was an opening on the further side, for a ray of light feebly penetrated the interior. Moving about in this dim illumination was our wasp, and after a little, we could see, quite distinctly, that she was digging a hole. This then is her method—to find some sheltered hiding-place where she may secretly make her nest, that no creature may know where her treasure is hidden.

We have twice seen a marginatus pick up her spider and fly with it backward for a long distance—as much as four or five feet. This recalls the wasp which is said to fly backward before a moving horse and catch the flies that are hovering over it.

P. marginatus is not troubled by any notion as to the family connections of the spider that she takes. Anything will do provided she is strong enough to overcome it and carry it to her nest. The effect of her sting is quite variable, since in some cases the victim was killed at once, while in others it was but little affected in the beginning and lived for eighteen or twenty days.