286 INSECTS AND MAN 



naive disregard for the truth, that a louse becomes a 

 grandfather in twenty-four hours. 



The crab louse appears to be a product of rather more 

 modern times than its confreres, though it is recorded by 

 Herodotus and by Aristotle. As its name implies, it some- 

 what resembles a minute crab in outline. This loathsome 

 creature, measuring from one-twentieth to one-tenth of an 

 inch in length, nominally inhabits the pubic regions, though 

 it may extend to the beard, armpits, eyebrows, and even 

 eyelashes ; it does not attack the head, perhaps because its 

 enormously developed claws are not fitted for clasping the 

 fine hairs of that region. The adult is nearly white, with 

 a dark patch on each shoulder, and reddish legs and claws. 

 It is even more prolific than the head and body lice, and, 

 when present in large numbers, is probably the cause of 

 the mysterious disease known as phthiriasis. 



FLY PAKASITES 



Precise details concerning the bot flies of man may be 

 said to be "wropt in mystery." The great naturalist 

 Linnaeus, in his Sy sterna Natura, first called attention to 

 the fact that the larva of a certain South American species 

 of fly had been found, from time to time, dwelling hypo- 

 dermically on some of the natives. Subsequent authors, 

 doubting Linnasus's description, dubbed the whole affair a 

 myth and attributed the attacks, if attacks they were, to the 

 ox warble fly. In 1822 Say actually received specimens 

 of the larvae from South America, and gave a detailed 

 account of them, and from that time onwards meagre 

 and spasmodic accounts of the human bot fly, known as 

 Dermatobia hominis (fig. 83), have been published, though 

 much still remains to be discovered. It is certain, at any rat9, 

 that the attacks of these insects are not confined to human 

 beings ; in fact, man must be considered as only an occa- 

 sional host, dogs, monkeys, and cattle being the subjects most 



