326 OUR HOUSEHOLD INSECTS 



feeds and lives very high, and that makes it so saucy, as 

 to pull any one by the ears that comes in its way, and 

 will never be quiet till it has drawn blood." Whatever 

 we may think of the good taste of this passage, and the 

 quaint conceit it contains, it is evident that personal 

 cleanliness was not considered in the days of the Stuarts 

 a matter of such vital importance as it has come to be 

 regarded by respectable society in the Victorian era, and 

 visions of the shady side of domestic life in the time of 

 the " Merry Monarch " are called up, which it is as well 

 to drawva veil over. 



Man is not exceptional amongst mammals in harbour- 

 ing these vermin, he is but in the same category with 

 the rest ; for it seems to be the rule, from elephant to 

 mouse, largest to least, that some member of this group 

 of parasites should be attached to each species ; and even 

 aquatic mammals, such as the seal and walrus, do not 

 escape their attacks. But just as the human flea is not 

 the same as those of other animals, so human lice are 

 distinct from those which infest the lower mammalia, 

 and indeed each species of mammal may be expected 

 to have its own distinct parasite. Man, then, is not 

 exceptional in suffering from these parasites, but rather 

 in having to some extent, as has taken place amongst 

 civilised nations, shaken himself free from them. 



Of these disgusting insects three species are known to 

 infest human beings, the head-louse (Pediculus capitis\ 

 the body-louse (P. vestimenti), and the crab-louse (Phthi- 

 rius ingumalis). The first is the kind that occurs most 

 commonly, and the last is the rarest. The two Pediculi 

 are very much alike, the body-louse being best distin- 

 guished by the locality in which it is found, and by its 

 larger size ; the Phthirius is very different from both. 

 Taking as our type the commonest species (Fig. no), we 



