vni] RAT-FLEAS AND BAT-FLEAS 107 



takes the first opportunity that comes of getting on 

 to its host. Bats are seldom found to be much 

 infested with fleas ; for this reason, bat-fleas are 

 somewhat difficult to obtain and many of the species 

 that are known are extremely rare. 



The hosts of bat-fleas, obviously, vary more as to 

 the surroundings which they inhabit than almost any 

 other animals. They are found from the equator 

 north and south to the Arctic circle and the straits 

 of Magellan, in the densest tropical forests and flitting 

 round the barest northern buildings. Some pillage 

 the rich fruit gardens of India, whilst other smaller 

 bats work hard for a precarious diet of gnats round 

 a Siberian village. Two sharply divided groups of 

 bats exist : (1) The fruit-bats (Macrochiroptera) with 

 flat molar teeth adapted for a vegetable diet. These 

 are found in the warmer parts of the Old World but 

 not in America. (2) The insectivorous bats (Micro- 

 chiroptera) whose molar teeth are equipped with 

 sharp cusps for biting their animal food. These have 

 an almost world-wide distribution, and one species at 

 least ranges within the Arctic circle. The same fleas 

 are not as a rule found on the large fruit-bats as on 

 the small ordinary bats. But some bat-fleas have an 

 extensive range. The same species has been taken 

 from different bats of various kinds in Sierra Leone, 

 in Madagascar and in Java. 



All bat-fleas are blind. This absence of eyes, in 



