v] HUMAN FLEA AND OTHER SPECIES 71 



first genal spine, or first tooth in the head-comb, is 

 shorter in the dog-fleas of both sexes than it is in the 

 cat-fleas. The abdominal stigmata appear to be 



Fig. 7. The head of a female dog-flea (above) and a female 

 cat-flea (below) to illustrate the difference in shape. 

 In the males the difference is less strongly marked but 

 quite perceptible. From Novitates Zoologicce, Vol. xn, 

 January, 1905. 



larger in a dog-flea than in a cat-flea, and there are 

 differences in the bristles which seem to be constant. 



