344 



APPLIED ENTOMOLOGY 



optera, and also Spiders in their early stages, at least in most cases, and 

 a few are injurious as they are parasites of beneficial forms. Thus 

 among the Coleoptera parasitized are some of the Lady beetles. In 

 other cases it is the parasites themselves which are parasitized. In 

 this last case the destruction of a beneficial parasite by another makes 

 the latter an injurious insect. There are also some which appear to 

 attack the parasites of the parasites, which places these last as beneficial 

 in their turn. Primary parasites attack non-parasitic forms; secondary 

 or hyperparasites attack primary ones; tertiary parasites attack the 

 secondary ones, etc. 



FIG. 359. FIG. 360. 



FIG. 359. An Evaniid (Brachygaster minutus Oliv.), about five times natural size. 

 (Modified from Kieffer.) 



FIG. 360. Example of an Ichneumon Fly (Ophion), natural size. (Original.) 



The importance of the Ichneumon flies as parasites is very great as 

 they are abundant and destroy enormous numbers of injurious forms 

 each year. One group devotes its attention to plant lice, puncturing 

 the bodies of these insects and laying an egg in each puncture. The 

 tissues of the plant louse are fed upon by the parasite and the body of the 

 host gradually becomes brown, swollen and rather globular, and it dies, 

 holding on to the place where it was feeding at the time of its death. 

 After pupation within the body of the host, the adult parasite cuts a 

 circular opening in the surface of its host and escapes, and plant lice 

 bodies, swollen, brown, and with a hole in each are abundant when these 

 insects occur in large numbers. As each parasite obtains all the food 

 necessary for its entire development from the body of a single louse, these 

 insects are naturally extremely small (See Figs. 199 and 200). 



Another Ichneumon fly which is often noticed has a body an inch and 

 a half or more long and an ovipositor often over three inches and which has 

 been recorded in a few cases as nearly six inches in length. There are two 

 kinds of about this size, one with a black body and a few yellow spots, 

 the other brown with yellow markings, while other and smaller species 

 also occur. These insects attack the Horn-tails already described and 



