vin] RAT-FLEAS AND BAT-FLEAS 103 



British Islands and the other countries of Northern 

 and Central Europe. It readily bites man, and there 

 is no reason to suppose that, other conditions being 

 equal, it would not be as efficient an agent in 

 spreading plague as the last species has been shown 

 to be in India. 



3. Ceratophyllus anisus. This is a closely allied 

 species of rat-flea which replaces the last in China 

 and Japan. 



4. Leptopsylla musculi. This is the mouse-flea 

 and it is as widely distributed over the globe as its 

 host. From mice it frequently moves to rats, and 

 it has been found on them in various parts of Europe, 

 America, Australia, and Japan. It occasionally bites 

 man, but evinces little inclination to do so. 



5. Ctenophihalmm agyrtes. This flea is commonly 

 found as a parasite of voles and field-mice. When 

 farm-rats take to an open life in the fields they pick 

 up this species from the rustic rodents. In Hertford- 

 shire, Hampshire and Suffolk one half the fleas from 

 rats, collected in farmyards and hedgerows, were 

 found to belong to this species ; but whether it is 

 as common on rats all over England is unknown. 

 It appears not to bite man. A closely allied flea 

 (Ct. assimilis) is found in central Europe on field- 

 mice and equally on rats which live under the same 

 conditions. It has not been found in England. 



The principal occasional parasites of rats are 



