47 6 



Saw-flies, Gall-flies, Ichneumons, 



a small part of the whole family. The parasitic habit, only slightly indulged 

 in among the Cynipidae, is, however, the prevailing one of a majority of Hy- 

 menopterous insects. Although we commonly think of bees, ants, and wasps 

 as the typical Hymenoptera and as constituting the bulk of the order, it is a 

 fact that in point of numbers they are far outclassed by the parasitic forms 

 whose life is, like that of the social Hymenoptera, also highly specialized, 



FIG. 668. Caterpillar of a moth killed by Hymenopterous parasites, the adult parasites 

 having issued from the many small circular holes in the body-wall. (After Jordan 

 and Kellogg; twice natural size.) 



but along a radically different line. In a half-dozen families, including the 

 largest in all the order, nearly every species is a parasite and a parasite of 

 other insects. Indeed the chief agents in keeping the great insect host so 

 checked that plants and other animals have some food and room on the 

 earth are insects themselves. With all the artificial remedies man has 

 devised and now uses against the attacks of insect pests, the all-important, 

 constantly effective check on these pests is their parasitization by the host 

 of species of the Hymenopterous families of Chalcididae, Braconidae, Proc- 

 totrypidae, Ichneumonidae, etc. 



These parasitic Hymenoptera are only rarely collected by amateurs, 



FIG. 669. Larva of a sphinx-moth with cocoons of a parasitic ichneumon-fly. 



(Natural size.) 



although caterpillar-breeders always get acquainted with some of them, to 

 their dismay and disgust. But even if collected, the unsettled state of their 



