456 MEDICAL ENTOMOLOGY 



Ctenocephalus felis* Bouche, the cat flea, the head of the female is long 

 and pointed, while that of the female of C. canis, Curtis, is more rounded. 

 The difference in contour is less marked in the males, but is present. 

 In each species there are eight spines on the genal comb, but in both 

 sexes of canis the first spine and the one at the genal angle are shorter 

 than the corresponding ones in felis. The hind tibia of canis bears two 

 bristles at the edge, situated between the fifth and the dorsal apical 

 pairs, while in felis there is only one bristle and a small hair in this 

 situation. The mid-tarsus of felis is more slender and the second 

 segment narrower than in canis. The males can be distinguished by the 

 structure of the ninth tergite. The clasper or ' moveable finger ' of felis 

 bears more hairs than that of canis, and in the latter the manubrium is 

 slightly swollen (Plate LIV, fig. 3). In addition to these characters, the 

 number of bristles on the metathoracic episternum, the epimerum, and 

 the inner side of the hind femur, is slightly greater in canis than in felis. 

 Both species are said to be widely distributed and common, though 

 little seems to be known with regard to the relative frequency of their 

 occurrence. It is by no means the case that canis is found on the dog 

 and felis on the cat, for they both occur on either animal and on many 

 others beside, notably on the various species of rats which frequent the 

 same localities. Both will bite man on occasion. In Madras the com- 

 mon flea on the street dogs is C. felis, while canis occurs on the jackal. 

 According to Mr. Rothschild, canis is more abundant in temperate coun- 

 tries than in the tropics. 



GENUS CERATOPHYLLUS, CURTIS. 



This is a very large and widely distributed genus, the species of which 

 are found chiefly on rodents and other small mammals, some also oc- 

 curring on birds. Many of the species are found on moles, and in 

 America on squirrels and ground rats. The important forms are those 

 which have been found on rats and house mice. Of these C. fasciatus 

 is the common flea found on rats in Europe, while C. penicilliger 

 is common on field mice in England. C. fasciatus can be distinguished 

 by the shape of the moveable process of the clasper, the proximal edge 

 of which is angulate, and by the sinuous edge of the seventh abdominal 

 sternite. It has eighteen to twenty spines on the pronotal comb. 

 C. acutus, Baker, is the common flea of the Californian ground squirrel. 



Further distinguishing characters of the genus are as follows. Three 



* The cat and dog fleas are frequently called Ctenocephalus (Pulex) serraticeps felis, 

 and C. serraticeps canis. This is incorrect ; the name serraticeps should be dropped. 



