INSECTA 



113 



material, such as may accumulate about the abodes of 

 animals. Adult fleas feed on various warm-blooded ani- 

 mals. Dogs, cats, rats, men and other animals have 

 characteristic species associated with them. Most spe- 

 cies of fleas prefer a particular host/ but will feed on others 

 if hungry. 



Fleas have lately excited interest among medical men 

 because they have been found to be carriers of several 

 diseases. The rat flea, Xenophylla cheops, carries the 

 bubonic plague. This dreadful disease has several times 

 become established on the borders of the United States, 

 being introduced on vessels from foreign countries. Pre- 

 ventative measures consist in the destruction of rats and 



Fio. 55. A flea with its eggs, larva, and cocoon. 



other rodents, placing metal "rat guards" on the cables of 

 ships while in port, fumigation, etc. Where the plague has 

 become established, regular campaigns must be waged. 

 In California the government has recently hired squads 

 of men to destroy rats and ground squirrels. In New 

 Orleans the houses in certain parts of the city were com- 

 pletely destroyed and replaced by " rat-proof" buildings. 

 Order 18. Coleoptera, Beetles (Fig. 56). This order 

 approaches the Diptera and Lepidoptera in numbers. 

 There are about twelve thousand species in the United 

 States. Beetles have four pairs of wings, the first pair 

 forming hard sheaths, or elytra, which cover the mem- 



