20 GENERAL ZOOLOGY 



part is a hardened portion called the scraper (Fig. 9, B, 2). The 

 noise is produced by raising the anterior wings and rubbing the 

 rasp of the right wing against the scraper of the left. Fig. 9 



shows one of the 

 species common 

 in the eastern 

 United States. 



The mole-crick- 

 ets ( Grryllotal f/ pa. 

 FIG. 10. Mole-Cricket. Slightly enlarged . 



tig. 10) are bur- 

 rowing insects, which show interesting adaptations to sub- 

 terranean life. The fore legs are thickened and adapted to 

 burrowing. Roots are easily cut in two by means of a shear- 

 like motion of the joints of each front tarsus against the 

 teeth of the tibia of that leg. For this reason mole-crickets, 

 when numerous, are sometimes a serious pest. The female 

 mole-cricket watches over her eggs and, when they are hatched, 

 feeds the young till the first molt. Mole-crickets are found 

 both in America and Europe. 



Cockroaches. The cockroaches are cosmopolitan forms, 

 some of which infest our houses, where they feed on both 

 animal and vegetable matter. They are dark-colored, flattened 

 insects, which depend upon their legs for escape, although 

 most of them possess wings. Their flattened bodies make it 

 easy for them to hide in crevices, whence they come out at 

 night to feed. The female carries her eggs about with her 

 in a large case till the young are nearly ready to appear. 

 It has been asserted of some species that the mother assists 

 the young in escaping from the egg-case. Just before hatch- 

 ing, the distance between the lateral surfaces of the young 

 cockroach is only one third of the diameter from the dorsal 

 to the ventral surface. Soon after hatching, it assumes the 

 dorso-ventral flattened form of the adult, an adaptation to 

 their life in concealed places. Fig. 11 shows the German 



