THE AMERICAN ENTOMOLOGIST. 



85 



some fastidious persons as offensive and dis- 

 gusting, and beneath the dig-uity of us great 

 Lords of the Creation. But, as the all-wise 

 Autlior of nature has taken the pains to create 

 these little animals, and organized them in so 

 l)erlect a manner, that life is to them as much a 

 source of happiness as it is (o us, we can see no 

 good reason why it should be degrading to the 

 Creature to study even these, the humblest and 

 lowliest works of the great Creator. 



Among the vast aud extensive class of insects 

 tiicre are no less than eight distinct species that 

 luey exclusively, or almost exclusively, upon 

 num. Of each of these— which come more im- 

 mediately within the scope of this joiinial— we 

 shall now give a short account, and we shall 

 then brietly refer to some ten or twelve other 

 species which are known to inhabit the human 

 body. These last are not true insects, though 

 they belong to the same great group of ringed 

 animals as insects do, and we shall therefore 

 pass them over with comparative brevity. On 

 the whole, we may- safely affirm that man is in- 

 fested by neai'ly a score of dift'erent parasites. 



Tlie Eight True Iiiset'ts that are Parasitic on Man. 



The IIkad-i.olse ( I'edicHlits Inuminus, Linn.) 

 is seldom found upon adults, but inhabits almost 

 exclusively the heads of children. Its eggs, 

 which are popularly known as "nits," arc 

 glued to the hairs among which it dwells, and it 

 is solely by means of these eggs that the species 

 is propagated. The vulgar belief that dirt and 

 tiltli breed lice is a vulgar error; although, of 

 course, these creatures increase with greater 

 rapidity on a dirty head than on a clean one, 

 because, on the former they meet with a more 

 abundant supply of their appropriate food. 



Stephens, a British entomologist of no very 

 high standing, has classified the louse of the negro 

 {I'eiUciilns nigritarnm) as a distinct species 

 from that of the'white man ; whence it might be 

 riasonably inferred that the negro and the 

 white man sprang from a different origin. But 

 we are informed by a gentleman who formerly 

 owned slaves in KeutucUy, that the little negro 

 boys iu that State used commonly to communi- 

 cate the vermin in tlieir heads to their white 

 playmates, and that when thus communicated, 

 the race increased and multiplied with great 

 rapidity, which fact pretty effectually demolishes 

 Stephens's hypothesis. For it is a very general 

 law, that the same species of louse cannot thrive 

 upon the bodies of two distinct species of 

 animals. 



The Body-louse {Pediculus cercicalis,lAim.) 



inhabits more peculiarly the nape of the human 

 nock, whence is derived its scientific appellation, 

 which, when translated, means '■ neck-louse." 

 It very commonly, however, is found upon any 

 part of the body which is not covered with a 

 dense growth of hair, attaching its "nits" or 

 eggs to the short scattering hairs which grow 

 upon such parts. This is the species, which, dur- 

 ing the late war, infested so grievously both 

 Union aud Eebel soldiers, ft-om whom it received 

 the characteristic name of "gray-back." It differs 

 IVom the Head-louse in having a distinct 

 blackish stripe, commencing between the hind 

 legs and reaching about two-thirds of the way 

 to the tip of the abdomen. The male is dis- 

 tinguishable at once from the female by having at 

 the tip of the front shank {tibia) a very robust 

 blunt-pointed spur, which is almost as long as 

 the shank itself. As this species attaches itself 

 very commonly to the linen of the individual 

 man whom it inhabits, it is manifest that those 

 who change their linen with reasonable fre- 

 quency, and have that linen washed in scalding 

 hot Avater, cannot be long infested by it. The 

 reason that it was so prevalent in the late Avar 

 was, that the soldiers, from the necessities of the 

 service, were unable to wash their clothing as 

 often as they would have done at home, and 

 nineteen times out of twenty had nothing but 

 cold water to wash it in. Now, almost every 

 species of insect will revive after an immersion 

 of several hours iu cold water, whereas water of 

 such a temperature, that you cannot bear your 

 finger in it for one second, will immediately 

 destroy any insect whatever that is immersed 

 in it. 



"We have ourselves carefully compared Body- 

 lice taken from the person of a negro with others 

 taken from the person of a white man, and can 

 perceive no difference whatever between the 

 two forms. 



The Crab-louse {Pediculus jnibis, Linn.) is 

 of a much more rounded and flattened shape 

 than the two preceding, from which it also 

 ditfers in sundry structural details, so that, since 

 the time of Linnteus, it has been referred by 

 some authors to a distinct genus {Phthirus). 

 It differs likewise very remarkably, not only 

 from the two preceding, but from all the true 

 lice that inhabit other species of mammals, so 

 far as they are known to us, in the following 

 respect: Like the other members of the family 

 to which it belongs, it attaches its eggs or "nits" 

 to the hair; but the young larvffi that hatch out 

 from these eggs, instead of living on the surface 

 of the skin, burrow under the scarf-skin or 

 epidermis, and remain there, feeding on the 



