MAMMALIA 457 



especially well represented in North America. The principal 

 types are the rats and mice, many of which are close followers 

 of civilized man; squirrels, chipmunks, and prairie dogs, 

 gophers, beavers, hares and rabbits, and porcupines. The 

 rodents feed on vegetable diet, and are destructive of many 

 plants and grains which man uses for food. Notwithstanding 

 man's efforts to destroy them their remarkable power of repro- 

 duction enables the more aggressive families to hold their own. 



\y/ 



FIG. 242. Flying Fox (Pteropus). U. S. Dept. Agriculture Year-book, 1898. 



Questions on the figure. What is the structure and arrangement of the wings 

 in such a form as this? To what order of mammals does this type belong? 



Rats are among the worst of mammalian pests. They follow 

 man closely and are very destructive of certain crops and of 

 stored grains and other foods. Beside this the rats, and in less 

 degree other rodents, are the carriers of the bubonic plague and 

 possibly other diseases. Fleas carry the disease from rats to 

 man. 



Order 8. Chiroptera (hand-winged; the bats). These are mam- 

 mals in which flight is made possible by a web or fold of the skin 



