SOME HUMAN PARASITES 285 



dark markings at the sides of the thorax and abdomen. 

 The female is larger than the male, being about one-eighth 

 of an inch long, and the last segment of her abdomen is 

 forked, whilst in the male it is rounded. There is no 

 sharp distinction between thorax and abdomen, the former 

 merging into the latter. The whole body is covered with 

 short, straight hairs. Several moults take place during 

 life, and maturity is attained in about a month. 



That different species of mammals harbour different 

 species of lice is easy to believe ; more remarkable is the 

 discovery that different races of mankind are the hosts of 

 distinct races of lice. The lice of Caucasians are nearly 

 white, those making their homes on West Africans and 

 Australian natives are nearly black, those on Hottentots 

 are orange, on Hindus smoke-coloured, on South American 

 Indians brown, and on Chinese and Japanese yellow ; 

 there are also distinct differences in the claws, correspond- 

 ing to the differences in texture of the hair of the various 

 races. The use of lice as food by certain uncivilised 

 peoples has already been noted. Sometimes, however, the 

 insects become too numerous; then certain races among 

 them the Australian natives, the Apache Indians, and the 

 Andamanese cover their heads and bodies with a layer of 

 mud, thereby reducing the population of their lively 

 companions. 



The adult body louse may be distinguished from the 

 head louse by the fact that its back is marked with dark 

 transverse bands; differences in habit also serve to dis- 

 tinguish the two species. The body louse only visits the 

 human skin when hungry, and spends the rest of its time 

 secreted in clothing, where also the eggs are laid. They 

 are exceedingly prolific, and it has been estimated that a 

 single adult female may have a progeny of eight thousand 

 in eight weeks, and in warm weather this number may 

 be largely exceeded ; in fact, the remarkable fecundity of 

 lice was once a popular byword, it being said, with a 



