PARASITICA 



551 



Notwithstanding the small size of Chalcididae, their remains 

 have been detected in the tertiary strata of both Europe and 

 North America. 



Fam. IV. Ichneumonidae (Ichneumon-flies). 



Wings with a well-developed series of nervures and cells; the 

 space on the front wing separating the second posterior 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. Larvae parasitic in habits. 



The Ichneumonidae form a family of enormous extent, con- 

 taining nearly 6000 described species. The study of the family 

 is but little advanced, owing to their parasitic habits and to 

 this bewildering multiplicity in their 

 specific forms. Most of the species, in the 

 larval state, live inside the larvae of Lepi- 

 doptera, and they thus keep the myriads 

 of caterpillars within bounds, the number 

 of these destroyed by Ichneumons being 

 prodigious. Some of the family are, 

 however, external parasites, and some are 

 known to attack Spiders and Insects of 

 other Orders than Lepidoptera. Their 

 antennae are not elbowed and are many- 

 jointed, the joints being closely compacted, 

 especially towards the extremity. This 

 character readily distinguishes Ichneu- 

 monidae from the families we have 

 previously considered. The ocelli are 

 well developed even in the apterous forms, 

 and are placed in a triangular position on the vertex. The pro- 

 notum is small in front ; and extends backwards at the sides to 

 the points of insertion of the front wings ; it is fixed to the 

 mesonotum. The wings (Fig. 367, A) have a more complex 

 neuration than those of most of the other parasitic Hymenoptera, 

 but are occasionally absent in one or both sexes of a species. The 

 metathorax is very small, and the middle and hind legs are 

 placed close together. The propodeum is very large, and is 



. 360. Lissonota setosa, ? . 

 Britain. Parasite of the 

 goat - moth, etc. (After 

 Katzeburg.) 



