FLEAS. 



13 



in the ' Cambridge Natural History.' They likewise 

 are apterous insects, and undergo an incomplete meta- 

 morphosis — that is, there is no distinction between 

 the larval, pupal, and imago states, except in size and 

 colour ; they are active during the whole of their 

 existence, and live upon the epidermal productions of 

 the skin and feathers. 



A. Fleas {Pulicidce) . 



A single species of Flea known as Pulex gallincB 

 or avium (fig. 2) lives upon the Fowl. This same 

 species seems to be common to most birds, for I have 

 found it in various nests, as recorded in my i Account 

 of British Diptera/ 



This pulex, like all its relations, is provided with a 

 sharp piercing-mouth, which they plunge into the 



Fig. 2. 



I u • 



Hen-Flea {Pulex avium). 



flesh. Their food consists of biood drawn from the 

 host. Fortunately for the host, they are not per- 

 manently parasitic, but partial ' guests/ only going 



