352 ECONOMIC ENTOMOLOGY 



metallic lustre. Sometimes they occur as secondary parasites on 

 primary parasites. The larvae live within other insects, often 

 within insect eggs and sometimes within larvae or pupae. The larvae 

 of Polygnotiis develop within the digestive tract of gall midges, and 

 Trichacis in the nervous system of the same midge. Telenomus is a 

 common form infesting the eggs of many butterflies and moths. Ano- 

 pedius is parasitic on the clover seed midge and the wheat midge, and 

 Platygaster on the Hessian-fly. The eggs of Proctotrypids are "ovate, 

 with a peduncle at the end." 



The neuration of the wings shows great diversity. As a rule the 

 hind wings are veinless. In some sub-families the veining of the fore 

 wings resembles that of the Braconids and the Chrysidids and Scoliids, 

 and in others the Chalcids. (Consult Ashmead's Monograph of the N. 

 A. Proctotrypidae and Brues' Serphoidea in Hymenoptera of Connecticut.) 



Family Pelecinid^ 



Pelecinus obturator Drury is a long black hymenopter (female 

 2-23^^ inches long), parasitic on white grubs (Lachnosterna) . It is 

 sometimes grouped with the Proctrypids under the Serphoidea. 



ICHNEUMONID^ (ICHNEUMON FlIES) 



These insects form an important group of parasites upon injurious 

 forms. The females lay their eggs either within or upon the host 

 larva, and the maggots feed within the host until maturity, feeding upon 

 its blood by osmosis through the skin; in some cases, by attacking 

 muscle tissues and the fat body, and getting air, probably by attach- 

 ment to the tracheae. Cocoons are often spun on the back of the host, 

 from which emerge the adults. Some common genera are Ophion 

 (light brown with compressed abdomen), parasitic on Polyphemus 

 larva, Thalessa (with a long flexible ovipositor) on Pigeon Tremex, 

 Pimpla conquisitor on the pupae of tent-caterpillars, the cotton-worm 

 and the Brown-tail, P. inquisitor on tussock caterpillars (see Howard's 

 Insect Book) , and Tragus parasitic on chrysalids of Papilio. 



Braconids (Braconid Flies) (Figs. 235 and 236) 



Braconids are, as a rule, smaller than the Ichneumons, but like the 

 latter are valuable parasites. A phidius and Lysiphlehus parasitize 



