The species of the genus Evania are believed to live at the expense of cockroaches (Blattidae), and to deposit their eggs in the egg-capsules of those Insects. The species of Gasteruption live, in the larval state, on the larvae of other Hymenoptera, more especially of such as form nests in wood. Very little is known as to the habits of the species of Aulacus, but it is believed that they are parasitic on members of the Hymenopterous families, Siricidae and Oryssidae. Only the most meagre details as to the life history of any of the Evaniidae have been recorded. The species of Evania are met with most freely where cockroaches abound, and are said, hence, to be frequently observed on board ship. Two or three species of each of the two genera Evania and Gasteruption occur in Britain. The latter genus is more widely known under the name of Foenus.[[483]]
Fam. IX. Pelecinidae.
Sexes very different; the female without exserted ovipositor, but with extremely long abdomen. Articulation between the femur and trochanter oblique and elongate, but without division of the trochanter.
Fig. 370.—Pelecinus polyturator, ♀. Mexico.
This family at present comprises, according to Schletterer,[[484]] only the three genera Pelecinus, Ophionellus, and Monomachus. The systematic position of the Insects is very doubtful, and their habits are but little known. Pelecinus polyturator (Fig. 370) appears, however, in the female sex, to be a common Insect over a large part of the warmer regions of the New World; it is in all probability parasitic in its habits, the elongate ovipositor of the female Ichneumon being in this Insect replaced by an extraordinary linear extension of the abdomen itself. Doubleday has recorded that he saw twenty or thirty specimens of this species that had perished with their elongated hind bodies inserted into the stem of a tree, from which they could not extricate themselves. On the other hand, Patton thinks they are parasitic on locusts.[[485]]
The male in Pelecinus has the proportions of the parts of the body normal, there being no elongation of the abdomen; it thus differs very much in appearance from the female. There seems to be very little to distinguish Pelecinus from Proctotrypidae. The undivided trochanters have led to these Insects being placed, by some, among the Aculeate Hymenoptera. This character, as we have already shown, occurs also in Proctotrypidae.
Fam. X. Trigonalidae.
Abdomen ovate, not separated by a pedicel from the thorax. Antennae twenty-five-jointed. Trochanters imperfectly two-jointed. Both the anterior and posterior wings provided with a well-developed neuration. Abdomen composed of only five apparent segments. Larva (in some cases) parasitic on Aculeate Hymenoptera.
