Useful Insects 



177 



245. Ichneumon Flies, of which there are many 

 kinds, are somewhat related to the bees and wasps. 

 The adult often feeds on nectar. The usefulness of this 

 class of insects is due to the fact that the young are 

 parasites. They do not secure their prey by force. 

 Instead of catching the insects and carrying them to the 

 young larvaB, their eggs are deposited in or on the bodies 

 of their victims, and there grow into grubs. The grubs 

 mature in or on the body of the hosts. The eggs of the 



Fig. 113. A, dead " green bugs," showing hole from 

 which the matured parasite emerges. The top 

 figure shows the lid still attached, but pushed 

 back; the bottom figure shows the parasite 

 emerging; B, principal parasite of the spring 

 grain-aphis or "green-bug;" adult female, highly 

 magnified. After Webster, United States Depart- 

 ment of Agriculture. 



parasite are most otten deposited in caterpillars, though 

 sometimes in the chrysalis, pupa, or on tne adult stage, 

 or even in the eggs of their hosts. Entomologists formerly 

 thought that each kind or species of parasitic insect 

 secured its food from just one or two kinds of hosts, 

 somewhat similar to that noticed in the parasitic fungi 

 previously mentioned (^[217). Recent investigations 

 have shown that there is much less restriction in feed- 

 ing habits among parasitic insects than was formerly 



