FLEAS 



(Order Siphonaptera.) 



The insects of this order, comprising all of the true fleas, 

 are all contained in a single family, the Pulicidae. They are all 

 wingless, the mouth-parts are formed for sucking, and the body 

 is compressed from side to side. The antennae are short and 

 thick, and are placed in depressions behind the simple unfaceted 

 eyes. The metamorphosis is complete. They are the greatest 

 jumpers known in nature. The fleas are like the mosquitoes, 

 comparatively few in number of species, but very abundant in in- 

 dividuals,andwell 

 represent in struc- 

 ture the degraded 

 form which is the 

 result of a semi- 

 parasitic life. 

 Thev prey upon 

 nearly all species 

 of warm-blooded 

 animals, some, 

 and in fact most 

 species of fleas, 

 passing readily 

 from one species of 

 animal to another. 

 Very many dif- 

 ferent kinds of 

 birds are infested 

 by Pulex avium, 

 while Pulex ser- 

 raticeps occurs all 

 over the world, 



a 



Fig. 112. Pulex serraticeps. 

 191 



(Author's illustration,) 



