CROP ENEMIES AND FRIENDS 



223 



These flies deposit their eggs on the larvae of other insects. The 

 maggots which hatch from the eggs enter the larvae and destroy 

 them by feeding on their juices. 



DRAGON FLY, DIFFERENT STAGED 



One kind of ichneumon fly locates the larvae which are working 

 as borers in trees. It makes a hole above them and deposits its 

 eggs on them. Other kinds destroy tent- 

 worm caterpillars, cabbage worms, and 

 other injurious larvae. From Spain there 

 has been imported a fly which is the 

 deadly enemy of the codling moth. It 

 is a wasp-like fly, about five eighths of 

 an inch in length, with two pairs of blue- 



TACHINA FLY 

 Larva at left and pupa at right 



black wings. It has a sharp, 

 impales the larvae. 



dagger-like sting with which it 



EXERCISE 



1. Observe and describe helpful insects. 



2. Catch some ladybird beetles and put them in a jar containing a 

 twig infested with plant lice. What do the beetles do ? 



