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Proctotrypoid Parasites — Part 2

As just stated, many of them develop in the eggs of other insects, such as butterflies, moths and true bugs, as well as grasshoppers. Many times students interested in rearing butterflies from the egg will be disappointed, instead of hatching out caterpillars to find numbers of the extremely minute black four-winged flies of the Proctotrypoid genus Telenomus, which make their appearance through minute perforations in the egg-shell. The eggs of the mourning-cloak butterfly (Euvanessa antiopa) are especially apt to suffer in this way.

Other Proctotrypoids live in the larvae of gall-flies, gall-gnats, of many kinds of flies, of butterflies and moths and beetles, and in plant-lice, and the eggs of spiders, as well as of bugs, butterflies and moths. Some of the species (of the genus Baeus) which live in spider eggs are very curious, wingless creatures of simple form.

The curious family Pelecinidae is placed in this super-family by Ashmead, and it forms an exception to the remainder of the insects with which it is thus associated from the fact that the trochanters are not divided; that is to say, they appear to be formed of but one segment. They are very curious creatures with an extremely long and slender abdomen, and look like Ichneumon flies. This elongation of the abdomen occurs only in the female sex. The male has a more normal abdomen. In their early stages they are probably parasitic upon the larvae of beetles. Pelecinus polyturator is our commonest species, and Professor Forbes states that he has bred it from May beetle larvae.