CHAPTER XIV 



The Four-winged Parasites 



It is fortunate for mankind that almost all species of in- 

 jurious insects have insect enemies that destroy them. 

 These insect enemies are divided into two groups as regards 

 the methods by which they kill their victims. There is no 

 hard and fast line to be drawn between these groups, but 

 in general we may safely say that the insects which destroy 

 other insects are either parasites or predaceous insects. As 

 a rule, the parasites develop in the larval state within the 

 bodies of their victims, and, as a rule, the predaceous insects 

 feed, sometimes during the earlier stages, sometimes during 

 their adult stage, and sometimes during both, upon their vic- 

 tims, attacking them from the out- 

 side either by thrusting a pointed 

 beak through the skin and sucking 

 their lifeblood, or else by devouring 

 them bodily. 



The Ichneumon Flies 



One of the most important groups 

 of parasitic insects is that of the 

 Ichneumon Flies. These are slen- 

 der-bodied, more or less wasplike 

 creatures, with four wings, long 

 antennae, and well-developed legs 

 You may very often see them run- 

 ning rapidly over the surface of leaf or bark, in search 



174 



Ichneumon Fly ovipos- 

 iting IN Cocoon 



adapted for running. 



