70 THE FLEA [OH. 



are dealt with later on. Among the commonest fowl- 

 fleas which bite man are Ceratophyllus gattince and 

 C. gallinulce. Both species infest the nests of many 

 common passerine birds besides the domestic fowl. 

 A common parasite of the pigeon is C. columbce, 

 which also bites man. 



Dog-fleas and cat-fleas frequently transfer them- 

 selves to man. It has been asserted that the flea of 

 the dog and the flea of the cat are indistinguishable. 

 Several great authorities on fleas, such as Dr Carlo 

 Tiraboschi in Italy and Mr Carl Baker in the United 

 States, have maintained that the differences between 

 Ctenoeephalus canis and Ct. felis were unreliable 

 and that they are not distinct species. Mr Charles 

 Rothschild has, however, shown that the two species 

 are abundantly distinct. The males of these two 

 insects can be readily distinguished from each other 

 by differences exhibited in their respective sexual 

 organs. The females can be distinguished, at a 

 glance, by the different shape of their respective 

 heads. Fig. 7, which shows the head of a female 

 dog-flea above and of a female cat-flea below, illus- 

 trates this. It will be seen that Ct. felis has a much 

 longer and more pointed head than Ct. canis. In the 

 males the difference in the shape of the head is less 

 strongly marked, but is quite perceptible. There are 

 several minor differences in addition which serve, but 

 less clearly, to distinguish these two insects. The 



