THE FOUR-WINGED PARASITES 187 



Aphides or Plant Lice 



1. Find some colonies of aphides on some shrub, tree, or herb. 

 They are commonly abundant on cabbage leaves. Look carefully for 

 brown inflated specimens. These are parasitized. - 



2. Place some of these parasitized aphides in small vials and rear 

 the adult parasitic fly. Notice the hole through which it comes. 



3. Read Life Histories of American Insects, pages 197-199. 



Sphinx Caterpillars 



1 . Look over tomato vines, grapevines, Virginia creeper, and other 

 plants to see if you can find any large sphinx caterpillars bearing on 

 their backs the cocoons of microgaster flies. If you find any, place each 

 in a vivarium. 



2. Notice whether the parasitized caterpillar eats and how long it 

 lives. When the flies emerge, notice whether they are all the black 

 microgasters which are the primary parasites or whether there are some 

 bright-colored chalcid flies, which are secondary parasites. 



3. Read these references : — 



Life Histories of American Insects, pages 181-188. Nature Biographies, pages 

 122-131. 



