v] HUMAN FLEA AND OTHER SPECIES 69 



Sandy places such as sea-beaches and picnic 

 grounds, where humanity congregates for pleasure 

 or business, frequently swarm with this species of 

 flea waiting an opportunity to feed. The larvae are 

 bred in the sand and feed on organic refuse. 



The genus most closely allied to that which con- 

 tains the human flea consists also of a single species 

 only. It is a large flea (Pariodontis riggenbachi) 

 found on porcupines all over Africa and in India. 



Mankind is, occasionally, bitten by a variety of 

 other species besides Pvlex irritans. In hot countries 

 the chigoe (Dermatophilus penetrans) is a serious and 

 troublesome pest, particularly to bare-footed people. 

 In temperate regions there are rat-fleas, cat-fleas, 

 dog-fleas and bird-fleas which occasionally transfer 

 themselves to man and feast on his blood. But, on 

 the whole, hunger and propinquity rather than free 

 inclination seem to actuate these fleas of which man 

 is only the occasional host. There are besides very 

 numerous species which have never under any cir- 

 cumstances been known to bite man. There is no 

 doubt that some persons are more attractive to fleas 

 than others. The reason for this we do not know. 

 It may depend on the tenderness of their skin, the 

 quality and taste of their blood, or their personal 

 smell, or possibly all three combined. 



The various forms of rat-flea which are important 

 in carrying plague from rodents to the human race 



