Wasps, Social and Solitary

by George W. Peckham; E. G. Peckham

While standing guard over the caterpillar we noticed that it moved its head from side to side, showing that the first segment could not have been severely stung, as is usually the case in the work of urnaria.

In five minutes the wasp returned, and, with the air of feeling that everything was right, picked up her burden and carried it laboriously through the remaining bushes and then through the grassy space that edged the garden, as far as the rail fence which separated this part of the grounds from the woods. Without a pause she climbed on to this fence to the height of the second rail, passed through, and flew down on the further side. Here she paused a moment, perhaps to take breath, and we looked at each other in some dismay. Whither was she leading us? We had now been following her for over an hour, and she looked equal to as much again as she started off once more, rapidly this time, for the grass was short here and the traveling was easy. Soon, however, it became evident that things were going wrong, although we could not determine what was the matter. The caterpillar was laid down while the wasp absented herself for six minutes. She returned and carried it for fifteen minutes, and then left it for half an hour. Once more she came back, and carried it for ten minutes, and then she flew away. It was now four o’clock, and we had been following her since two. We watched over the caterpillar for an hour longer, but saw no more of the wasp.

Did she become discouraged at the magnitude of her task? It would have been a thousand times easier for her to have dug her nest close by the place of capture, but perhaps she had one larva already stored with her egg upon it. The caterpillar was carried two hundred and sixty-one feet while we watched her, with an unknown distance at each end to complete the line between the place of capture and the nest. She could scarcely have lost her way, since at every return she proceeded on her journey in one general direction without any hesitation. It seems probable then that she had hunted too far afield, and did not realize, when she started with her booty, what an undertaking it would be to carry it to the nest. We once saw A. vulgaris have a similar experience. She was running along with a small green caterpillar, but became discouraged either at the difficulty of finding her nest, or at the distance she had to cover. She would carry the caterpillar a little way, drop it, circle about a while, and then pick it up again; but finally she gave up the whole undertaking and flew away.

The affairs of Ammophila must frequently go wrong, since in still another of our few examples we saw much trouble and labor wasted. The wasp, in this case an urnaria, captured her caterpillar successfully and proceeded to carry it off. She was far from being in a hurry, going along for a foot or so, and then making a long pause, during which she would lay it down and either circle above it, perhaps to take bearings, or spend the time in cleaning herself off, stroking and smoothing every part of her body with the utmost care and deliberation. Her stops were so frequent and so lengthy that nearly an hour was occupied in going about twenty-five feet. When, at last, the nest was reached, the plug was removed from the entrance and the caterpillar dragged in, but almost immediately the wasp came out backwards with the point of an egg projecting from the extremity of her abdomen. She ran around and around the nest in a distracted way four or five times and then went back, dragged the caterpillar out, and carried it away. The egg came out further and further, and finally dropped on the ground and was lost. The wasp, carrying the caterpillar, led us a long dance, in a great semicircle over the field, coming back to the nest at last. Instead of going in, however, she was about to start off on another tour when we took her prey from her and placed it in the nest. The wasp remained in the neighborhood for over an hour, but finally disappeared. The nest was not closed, and when we dug it up on the following day it contained only the caterpillar that we had put in.

We could usually enter into the feelings of the Ammophiles and understand the meaning of their actions; but we were puzzled once, when we saw an urnaria that had stored her second caterpillar and closed her nest permanently, spend the rest of her morning in hunting. Why in hunting? She had not dug a nest, she could not lay another egg at once, she did not want a caterpillar, for when we offered her one she stung it and then left it lying on the ground. The sun was bright, the sorrel-blossoms invited her. Surely it would have been the part of a rational wasp to have passed the rest of the day in feasting and fun.

We have said that urnaria stores two caterpillars, but this rule is not without its exception. It was on the last day of the summer that on a visit to our dear and fruitful potato field, we came upon a wasp of almost double the ordinary size, that made, when flying, a loud hum that at once attracted attention. She was just completing and closing her nest, and we determined to watch and see what kind of a victim she would bring in, as it seemed improbable that this great creature would content herself with the ordinary fare of the species. The opening to the nest measured half an inch in diameter.

It was eleven o’clock when she flew away. At half past twelve she reappeared, coming from the direction of the woods, opened her nest, and took out a few more pellets. Then she flew to a bush which grew against the fence, three feet away, and following her quickly we saw an immense green caterpillar placed high up on a branch. It must have taken both strength and perseverance to lift this heavy weight so far from the ground. She seized it at once and carried it down, not flying, as these wasps sometimes do when they are descending with a burden, and then dragged it into her nest, where it fitted rather tightly. This nest was so shallow and so obliquely directed that the caterpillar was plainly visible after it had been taken in.

After she had laid her egg she crawled out, getting past the caterpillar with some difficulty, and closed the nest. There was certainly no room for any further store of provisions, and from the size of the caterpillar we judged that it would furnish sufficient nourishment even for the offspring of this wasp. We were, therefore, not surprised, upon opening the nest two days later, to find that nothing more had been brought. We have said that the wasp larvæ spend from six days to two weeks in eating. To be more exact, all that we watched, with the exception of the one which developed from the egg of this big creature, ate from six to eight days and then spun their cocoons; but this one seemed determined to reach the size of its mother, and ate continuously for fourteen days. Of course long before this time had expired the remnant of the caterpillar had become a dry, dark-colored mass which looked little likely to tempt the appetite, but the great larva ate away with unabated relish, gradually acquiring the color and almost the thickness of the caterpillar it had destroyed.

Ammophila polita, which we have never seen in the country, is very common in the sandy fields to the south of Milwaukee. On the tenth of September, in bright clear weather, we found half a dozen individuals working within a few rods of each other, their method being similar to that of A. yarrowii, described by Dr. Williston, and having an especial interest, as it shows a transition stage between the wasps that provide the store of food all at once and those that feed their young all through the larval period. Urnaria rarely flies with her prey; but this wasp, although her caterpillars, are not very much smaller, and she herself is no larger, carries her booty lightly on the wing, alighting only occasionally to run a few steps. She has to do more work than urnaria, taking five or six caterpillars instead of two, and this method of progression has the advantage of rapidity.