THEIR RELATION TO MAN 



215 



Fleas live in their adult stage on hairy, warm- 

 blooded animals, feeding on their blood, and their trans- 

 versely flattened form set with spines all directed back- 

 ward enables them to move about freely and quickly. 

 Their eggs are dropped in the dens or nests of their 

 hosts, and the larvae, which are slender, white and 



FIG 100. The common cat and dog flea: a, the egg; b, adult; c, pupa; 

 d, larva coiled in silken case; e, lar^a. 



worm-like, live on the dead and decaying animal and 

 vegetable matter always present in such places. In 

 houses, the common dog and cat flea is able to develop 

 its larvae in the material accumulating in the crevices 

 between floor boards and similar situations, and in the 

 adult stage almost any kind of flea will bite any warm- 

 blooded animal upon which it may happen to get, even 

 if not capable of maintaining itself there. So man, 

 though unfitted because of his hairless skin to serve as 



