HYMENOPTERA 



917 



more or less spherical, being greatly distended. These bod- 

 ies remain clinging to the leaves in the position in which 

 the insects were when they died. From each one there 

 emerges in due time an Aphidius. The parasite in emerging 

 cuts a very regular circular lid in the dorsal wall of 

 the abdomen of its host (Fig. 1151). We have 

 watched with much interest these little braconids 

 ovipositing in the bodies of plant-lice. When one 

 has selected a plant-louse in which to oviposit she 

 stands with her head toward it, and bending her ^ ^^^^ i 

 abdomen under her thorax between her legs she „. 

 darts her ovipositor forward into the body of the ^^' 



aphid. The species of this genus do not construct cocoons, but under- 

 go their metamorphosis within the dried skins of plant-lice. 



Family 

 ICHNEUMONIDiE 



The Ichneumon- flies 



This is a large fam- 

 ily including a great 

 number of genera and 

 species. Although it 

 includes some minute 

 forms the species are 

 mostly of considerable 

 size, and here belong 

 the larger of the para- 

 sitic Hymenoptera. 

 In this family, as in the preceding one, the costal cell of the fore 

 wings has been eliminated by 

 the coalescence of veins and the 

 venter is usually membranous 

 and has in dried specimens a 

 longitudinal fold. The ichneu- 

 mon flies differ from the bra- 

 conids in that Cell Mi and cell 

 ist M2 of the fore wings are 

 separate (Fig. 11 52), except in 

 a single genus, Pharsalia. For 

 distinguishing characters of 

 this genus see the table of 

 families. 



Students collecting Hymen- 

 optera will find many species of 

 ichneumon-flies ; and those at- 

 tempting to rear caterpillars 

 will be disappointed often by 

 the breeding of ichneumon-flies 

 instead of moths or butterflies. Fig. 1 153. — Megarhyssa lunator. 



Fig. 1 1 52. — Wings of an Ichneumon fly. 



