Wasps, Social and Solitary. George W. Peckham

      NEST OF OXYBELUS

      We find but meagre notes on the genus Oxybelus. Ashmead says that no observations have been made on the American species, but that in Europe they are found to burrow in sand and to provision their nests with dipterous insects. He says also that according to Verhoeff the species in this genus do not paralyze their prey by stinging, as they are unable to do so on account of the rigidity of the abdomen, but that instead they crush the thorax with the mandibles just beneath the wings, the centre of the nervous ganglia. He found in one nest a dozen flies, and all had the thorax crushed and were dead. In the case of our wasp we do not know how the flies were killed, but there was no crushing of the thorax. The larva devoured, in all, ten flies. At the time of its death it had probably finished the larval stage of its existence, since nine days had elapsed since the hatching of the egg. It may be that this period just before pupation is a critical point in the life history of a wasp, for we lost several of our nurslings at this time, and Fabre has noted that when, on account of the presence of parasites, the larva of Bembex rostrata had lacked something of its usual amount of nourishment, it perished miserably at the end of its larval stage, not having strength enough to spin its cocoon. No waspling in our charge ever died from lack of nourishment—on that score our consciences are clear; but it was difficult to make their conditions quite normal, and for this reason we may have been, indirectly, the cause of their death.

      The way in which our Oxybelus carries its prey is peculiar to itself. Bembex and Philanthus also hold their prey under the body, but use the second pair of legs, so that it does not project behind except at the moment of entrance into the nest. Quadrinotatus, as we could distinctly see, since she passed close to us several times in quick succession, clasps the head of her victim in the third pair of legs, and flying thus, with its whole body sticking out behind her, she certainly presents a very remarkable appearance.ill81

      APORUS FASCIATUS

      Aporus fasciatus is a dark gray species, and is less than half an inch in length. We were working one hot day in the melon field, when we saw one of these little wasps going backward and dragging a female of Mævia vittata which was much larger than she was herself. She twice left it on the ground while she circled about for a moment, but soon carried it up on to one of the large melon leaves, and left it there while she made a long and careful study of the locality, skimming close to the ground in and out among the vines; at length she went under a leaf that lay close to the ground and began to dig. After her head was well down in the ground we broke off the leaf that we might see her method of work. She went on for ten minutes without noticing the change, and then, without any circling, flew off to visit her spider. When she tried to return to her hole it was evident that some landmark was missing. Again and again she zigzagged from the spider to the nesting-place, going by a regular path among the vines from leaf to leaf and from blossom to blossom, but when she reached the spot she did not recognize it. At last we laid the leaf back in its place over the opening, when she at once went in and resumed her work, keeping at it steadily for ten minutes longer. At this point she suddenly reversed her operations and began to fill the hole that she had made, kicking in the earth until the entrance was hidden. She then glanced at the spider, selected a new place, and began to dig again. Surprisingly large pellets of earth were carried out, backward, and loose dirt was kicked under the body by the first legs. At the end of two or three minutes she paused and remained perfectly still for a time, considering the situation. Her conclusion was adverse to the locality, for she soon filled in the hole, looked once more at the spider, and started a third nest in a new place. This in turn was soon abandoned, as was also a fourth. The fifth beginning was made under a leaf that lay close to the ground, so that we could not see her at all. Fasciatus! had we had the naming of her she should have gone down the ages as exasperans! We had now watched her for an hour in the intense heat; the bell for the noonday meal had sounded, hunger and thirst had descended upon us, and most devoutly did we hope that she was suited at last, but no—after twenty minutes’ work this place also was abandoned, and a sixth nest started. This, however, was the final choice, and after forty-five minutes spent in digging, it was completed. As the spider was brought toward the nest it was left again and again while the nervous little wasp flew to the hole, went in, examined, and came out again. At last she backed in, caught the spider by the abdomen, and dragged it down. It was too big—the head stuck in the hole; but she pulled from below while we pushed gently from above, and it slowly disappeared. When she came out we opened the nest and took the spider. The egg was fastened to the middle of the left side of the abdomen. This one, as was also the case with a second and third afterward taken from fasciatus, was much less affected by the poison than is usual among the victims of solitary wasps, moving from the time it was taken, without any stimulation, and improving rapidly from day to day. Our second spider appeared to be blind, and died upon the sixteenth day, while the third had entirely recovered by the seventeenth day after it was stung, and was released. Fasciatus, then, probably depends upon packing her victim in tightly to keep it quiet.

      It was three days and a half before the egg that we had taken hatched. The larva developed rapidly, retaining its hold at the spot to which the mother had fastened it. The spider remained alive for six days, and the larva continued to grow for two days longer, when it died also, being at the time about two thirds grown. We had great trouble in protecting our growing larvæ from the inroads of fungi, and this was one of the many that perished from that cause.

      The next example of fasciatus that came under our notice was a remarkable contrast to the one that we have just described, being as slow and dignified as the other was nervous and hurried. She chose a place and kept to it, her steady labor being interrupted only by occasional visits to the spider; but it took her fifty minutes to complete the nest. When finished it was a small gallery running down obliquely for an inch and a half into the ground.

      The only habit that this species can claim as peculiar to itself is the strange and useless one of filling up the partly made nests that it is about to abandon. We have never seen the sense of order carried to so high a point in any other wasp.

      ill85