98 GENERAL ZOOLOGY 



tive to trees and fruit. They are always of minute size 

 but may be very abundant. The male is winged and 

 moves about freely. The female buries her beak in a 

 plant when young and never moves again. She has no 

 wings, and her body is covered by a secreted " scale." 

 She lays eggs which hatch beneath the scale. The young 

 females settle down near their mother, hence scale insects 

 spread rather slowly. The most important species eco- 

 nomically are the San Jose scale, introduced originally into 

 California but now found in most parts of the United States, 

 the cottony cushion scale, and the oyster scale. 



Cicadidce, the cicadas. The seventeen-year " locust" is 

 the best known representative of this family. The adults 

 sing discordant notes in trees during late summer and, after 

 mating, lay eggs in the twigs of trees. The larvae hatch 

 in about six weeks, drop to the ground, and live under- 

 ground for nearly seventeen years as ugly nymphs. The 

 nymph burrows about in the soil, feeding on roots and 

 humus. In the summer of the seventeenth year it crawls 

 out of the earth, climbs upon some plant, and an adult 

 cicada emerges from its skin (Fig. 47). 



Other insects belonging to this suborder are the tree- 

 hoppers, leaf-hoppers, lantern-flies, white-flies, spittle in- 

 sects, etc. The tree-hoppers and leaf-hoppers have peculiar 

 triangular or pointed heads. The spittle insects are found 

 within a mass of froth on low vegetation. 



Suborder 3. Heteroptera, the True Bugs (Fig. 48). 

 In this order the fore and hind wings differ; the former 

 being thick in front and thin behind; the latter, entirely 

 membranous. The peculiar fore-wings give the name 

 (Hemiptera half wings) to this whole order of insects, 

 though they are of course not characteristic of the first 

 two suborders. Several insects of great economic impor- 

 tance belong to this group, and many are common " water- 

 bugs." 



Among the aquatic Heteroptera are many with interest- 

 ing habits. All breathe air and must therefore have special 



