HYMENOPTERA 929 



to be found elsewhere. Species hibernating in logs often congregate 

 in groups of three to twenty in old beetle burrows and other cavities. 

 It is strange that Ichneimion idtimus and /. mendax, two of the com- 

 monest species collected in hibernation, have never in the author's 

 knowledge been found during the growing season, and their males 

 are apparently unknown. The genus Hoplismenus, with a conical 

 scutellum, is parasitic on nymphalid butterflies. The other species, 

 most of which have been included in the genera Ichneimion and 

 Anihlytcles, parasitize largely Noctuidae and Geometridae. 



The tribe Trogini includes large species about twenty millimeters 

 long with subconical scutella. Tragus vulplnus is a common red 

 species with black wings. The female oviposits into caterpillars of 

 swallowtail butterflies, and the adult parasite emerges through a 

 hole cut in the side of the chrysalid. Most of the other Trogini are 

 parasitic on hawk moths. 



Family TRIGONALID^ 

 The Trigonalids 



The family Trigonalidas includes a small number of rare species. 

 The adults look very much like sawflies. They differ from other 

 ichneumonoids in having a distinct costal cell in the fore wing and 

 more than fourteen antennal segments. Female trigonalids lay their 

 minute flattened eggs, about ten thousand in number, on the under- 

 side of leaves just back of the margin. In some species they are in- 

 serted into the leaf tissue. The eggs hatch when eaten with the 

 leaves by caterpillars or sawfly lar\^ae, provided that the shell is broken 

 in the process. The young larva enters the body cavity of the cater- 

 pillar and develops either as a primary parasite or as a secondary 

 parasite on some other parasite of its host. Some species are parasitic 

 in vespid nests. It is not known how these reach their hosts. One 

 species found parasitic in vespid nests has been observed to insert its 

 eggs into the margins of leaves. For a classification of the family 

 see Schulz, Genera Insectorum 1907, fasc. 61, 24 pp., 3 pis. 



Family AULACID^ 

 The Aidacids 



The aulacids have the abdomen attached high on the propodeum 

 far above the bases of the hind coxae as in the Gasteruptiidae and the 

 Evaniidae. They may be distinguished from these families by the 

 venation (Fig. 1155), the linear hind tibia, and the lack of a separate 

 petiolar segment to the abdomen. The ovipositor is somewhat longer 

 than the abdomen. There are three Nearctic genera: Pristdiilacus 

 with three or more teeth on the tarsal claws; Odqntdulacus with one 

 or two rather blunt teeth on the claws; and Aulacus (= Pamme- 

 gischia) with the claws apparently simple but each with a tooth at the 

 extreme base. Aulacus parasitizes the larvae of Xiphydria, a wood- 

 boring sawfly. The other two genera attack larvce of wood-boring 



