FLfcAS. 



233 



The common house flea of Europe is the Pulex irritans; that of the 

 Tinted States the Ctenocephalus serraticeps or dog flea. The flea that 

 is implicated with plague is the Pulex cheopis. It resembles P. irritans, 

 but is more yellow than brown in color. It also has a greater number 

 of bristles on the head. The ocular bristle runs above and in front of 



FIG. 72. Various pulicidae. i, Ceratophyllus fasciatus (rat flea); 2, Pulex- 

 cheopis (plague transmitting flea); 3, Ctenocephalus serraticeps (dog flea); 4, Sar- 

 copsylla penetrans (chigoe); 5, head of flea showing palps; 6, female of S. pene- 

 trans distended with eggs after burrowing under skin. 



the eye; that of P. irritans below. It is principally the flea of the M. 

 decumanus, the sewer rat; but the house rat, M. rattus, becomes in- 

 fected from coming in contact \vith the sewer rat in the basement. 



Sarcopsyllinae. 



Belonging to the subfamily Sarcopsyllinae, the Sarcopsylla 

 penetrans is of great importance in tropical countries. It is known as 

 16 



