2 LICE AND THEIR MENACE TO MAN 



Anoplura, on the other hand, have mouths so 

 modified that they are able to take only one form 

 of food, namely blood. This they obtain by 

 piercing the skin of their host and sucking at the 

 wound thus made. They do not eat one another 

 nor yet other insects, as an American doctor re- 

 cently stated they did, the form of the mouth 

 absolutely prohibiting this. 



Some blood-sucking insects, such as the mos- 

 quitoes, horse - flies, and tsetse - flies, are very 

 catholic in their tastes, taking their meal from 

 any warm - blooded, and sometimes even cold- 

 blooded, animal which happens to be convenient 

 when they are hungry. Others, such as the 

 fleas, are more particular, being in general 

 confined to one or a very few different kinds 

 of animals, but .on occasion biting another sort 

 if they chance to get on to it. Thus when 

 a rat dies of plague its fleas leave it and may 

 happen to get on to man, on whom they will 

 feed and thus infect with plague, though they are 

 not normally associated with him. The human 

 flea, on the other hand, also normally infests the 

 badger. The sucking lice, however, are very 

 highly specialised and are rarely found on more 

 than one kind of host, though there are records of 

 the human body-louse being found on pigs and 

 monkeys. Such cases are almost certainly acci- 

 dental. This specialisation affects several char- 

 acteristics of the lice, such as the adaptation of 

 the grip of their feet to hair of a definite calibre 



