When the filling of the nest was nearly completed, we caught the wasp, and after taking the spider, threw back the earth into the hole. Subviolaceus, who had watched the homecoming from a respectful distance, now felt that her turn had come, and descending upon the spot began to dig. Not finding anything, she shifted her position several times, and worked industriously, even returning after we had frightened her away. Sharp says that a Ceropales has been observed to oviposit on a spider, not while it was being carried in, but subsequently by entering the nest for the purpose; and the actions of subviolaceus pointed to similar intentions on her part. We have watched her for an hour at a time running into the open nests on the Bembex field, sometimes coming out again directly and sometimes remaining inside for several minutes. It is not likely that she would utilize the flies of Bembex, but it may be that she was looking for the Pompelid nests that are often made in the same locality. Scelestus did not notice subviolaceus, and it is difficult to see why a wasp should be disturbed by the presence of a parasite. In making and storing her nest she is the blind instrument of an impelling power; she knows what she must do, but not why she does it. Her descendants are in most cases as completely outside of her experience as her ancestors, and how should she guess that the presence of a certain fly or wasp means danger to her race? Of what happens to her egg after she leaves it she is so absolutely ignorant that she might easily look on with serene indifference at the destruction of her own larva by that of the intruder. In Astata we see, as might be expected, a calm tolerance of the visits of the Chrysis fly, but the uneasiness of scelestus herself at the sight of Ceropales and the valorous defense of Trypoxylon show more highly developed instincts. Bembex, too, deeply resents the presence of parasites, although after the deed is done she feeds their young without questioning their right to her care. Among bees, Andrena, and Nomada, which is parasitic upon it, are said to live on most friendly terms; but in other genera there is a deep-seated enmity between host and parasite.
THE HOME-COMING OF SCELESTUS
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In the literature of the Hymenoptera references have been made from time to time to certain wasps that cut off the legs of spiders or other creatures before storing them away; but observations on the subject have been rare and not very definite. Brehm, in the “Thierleben,” says that Agenia punctata builds nests of mud, and places in each cell one moderately large spider from which she has first removed all the legs. The most interesting notes on the subject have been made by M. Goureau, who gives an account of finding two spiders that had been mutilated by wasps, one of them having had all of the legs cut off, and the other all but the first pair. At another time a wasp that was flying near him let fall a spider, which he captured before it could be recovered by the owner. The wasp escaped, so that he could not determine the species, but the spider’s legs had been removed. He concluded that instead of stinging the spiders the wasps had mutilated them so that they could not run away. He does not seem to realize that death would certainly result from such an operation.[ill245a]
