564 HYMENOPTERA 



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 abdo- 

 men 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. 1 



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 Procto- 

 trypidae. 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 Procto- 

 trypidae. 



Pam. X. Trigonalidae. 



Abdomen ovate, not separated ~by a pedicel from the thorax. 

 Antennae twenty -Jive-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. 



This family is chiefly constituted by the very rare Insects 

 contained in the genus Trigonalys, of which we have one species 



in Britain. Although, so far as appear- 

 ance goes, they have little in common 

 with the parasitic Hymenoptera, and 

 look quite like members of the Acu- 

 leata, yet the late F. Smith found a 

 species in the cells of Polistes lanio, 

 thereby showing it to be of para- 

 sitic habits. Although some Aculeate 

 Hymenoptera are also of parasitic 



FIG. 371. Trigonalys maculi- habits, yet the characters of Trigonalys 



perhaps agree, on the whole, better 



with the Hymenoptera parasitica. The British species is very 

 1 Amer. Nat. xxviii. 1894, p. 895. 



