72 GENERAL ZOOLOGY 



They get their name from the habit the larvae have of hiding 

 under stones. 



Order 5. Isoptera (Fig. 39). The termites, or white 

 ants, have four leathery wings or are wingless, possess biting 

 mouth parts, and are heterometabolous. They are most 

 abundant in tropical countries where they do great damage 

 to timber and wooden structures. They never come out 

 in the light, but secretly dig burrows in wood until there 

 is nothing left but a thin outside shell which finally falls 

 into powder. Many species of termites make enormous 

 nests which contain thousands of individuals living as a 

 complex spcial community. Division of labor has been 

 carried so far that there are as many as eight different 

 castes in some species. These are females, males, workers, 

 soldiers, etc. The worker and soldiers castes are sexually 

 immature and may be either males or females. The 

 female breaks off her wings after mating so that she may 

 not stray from home. When mature she is a big helpless 

 egg-laying sac, and must even be fed and cleaned by her 

 nurses. She grows to be a thousand times as large as her 

 mate. 



Orders 6, 7, 8, 9. Corrodentia, book-lice and bark-lice; 

 Mallophaga, biting bird lice; Thysanoptera, thrips; Euplex- 

 optera, earwigs. All these insects have biting mouth parts, 

 and are heterometabolous, except the Thysanoptera which 

 have mouth parts somewhat modified for sucking and a 

 peculiar metamorphosis in which there is a resting stage. 

 Different species of thrips are pests on onion, wheat, grass, 

 and fruit. 



Order 10. Orthoptera (Fig. 40). The cockroaches, 

 walking-sticks, mantids, grasshoppers, locusts, katydids, 

 and crickets are included in this order. These insects all 

 have biting mouth parts and are heterometabolous. Most 

 of them have four wings; the anterior pair being straight 

 and leathery; the posterior pair, membranous and folding 

 like a fan. There are six important families: 



Family 1. Blattidce; cockroaches. These insects have 



