128 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVI. 



Fam. VII. Iclmeumonidae— Ichneumon Flies. 



The Ichneumons are Insects with a long slender body and many-jointed 

 antennae. The wings have a well -developed series of nervures and 

 cells in them ; the space on the front wing separating the second pos- 

 terior cell from the cubital cells is divided into two cells by a transverse 

 veinlet. The abdomen is attached to the lower or posterior part of the 

 median segment. The female has usually a long protruding ovipositor. 

 (See fig. 49.) These Insects are parasitic in their larval stages. 

 The egg is deposited by the mother in or on or near the body of the 

 grub. The larva on hatching out is a little white legless maggot which 

 feeds upon the fatty tissues of its host, the latter eventually dying of 

 exhaustion, although it may have sufficient strength to turn into 

 a pupa first. When full fed the ichneumon grub spins itself up 

 into a cocoon. This it may do inside the now dying or dead host 

 larva, or it may attach the cocoon to the outside of the skin, 

 or it may lie free outside the latter. It often happens that two 

 or more eggs are laid upon the caterpillar by the ichneumon fly 

 and then several cocoons are obtained from the dead caterpillar 

 or from the pupa into which it has changed. Owing to the peculiar 

 methods of existence of its members it will be obvious that this 

 family performs a very important service to man by keeping down 

 defoliating larvae and stem and wood-boring pests and, in fact, Insect 

 pests of all kinds. At the same time it is also injurious to some 

 extent owing to the fact that it also lays its eggs and kills off 

 useful predaceous and parasitic Insects. From the little we already 

 know of the life histories of some of our Indian Ichneumonidse it 

 has become evident that the family is of the very first economic 

 importance in this country, and its study, therefore, for this reason 

 alone, is strongly advocated. 



The members of the genera Rhyssa and Thalessa are among the most 

 remarkable of the ichneumon flies. These Insects have ovipositors of 

 two to four inches in length (fig. 49) and are parasitic upon species 

 of the family Siricidse which, as above described, live in solid wood. 

 The following is a note on a portion of the life history* of a new 

 and undescribed species of Rhyssa, Rhyssa sp. f which is parasitic 



* Vide foot-note on p. 119. 

 f Col. C. T. Bingham hopes to shortly describe this species for me. 



