The egg, which was laid just before nine o’clock on the morning of August seventh, hatched at a little after nine on the morning of August eighth. The larva began to eat at once, and devoured all the inside of the thorax and abdomen of the fly to which it was attached, in the first twenty-four hours. On August twelfth it had reached the sixth fly, and we supplied it with three more. On August fourteenth these were gone, and we again replenished its larder, this time with two flies. The larva had partly eaten these when something went wrong. Its appetite failed, and on August sixteenth it died.
On further acquaintance this wasp lost none of her charm,—indeed, she gained in interest from the almost human curiosity that she showed about the affairs of other people. Where several were living close together one of them would sometimes stop digging her own nest to perch on a weed and watch the labor of another, and we once saw an especially inquisitive character burrow through the closed door and enter the home of her next-door neighbor.
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]
