INSECTA 



97 



all of small size, and often occur in great numbers on 

 plants. In spring and during the summer certain females, 

 the "stem mothers," bring forth living young which have 

 developed from unfertilized eggs. In the autumn male 

 individuals appear, and fertilized eggs are laid which pass 

 through the winter. Several different kinds of individuals 



FIG. 47. Homoptcra. At the left are plant-lice, or aphids, one being de- 

 voured by a lady-bird beetle (not Homoptera) ; above are leaf-hoppers and 

 "brownie bugs," or tree-hoppers; on the tree trunk is a cicada, or seventeen- 

 year locust, which has just emerged from its nymphal skin, and two species of 

 scale insects. 



are often present in the same species: winged, wingless, 

 woolly, smooth, large, small, etc. The grape-phylloxera 

 is a destructive species which perforates the roots of plants 

 and starts diseases; green-fly on wheat, and the woolly 

 apple aphis are also important. 



Coccidce, scale insects. These are particularly destruc- 



