HEMIPTERA. 165 
The eggs—“‘nits”—are attached to hairs by a glue-like substance, and 
the young lice when hatched resemble the adults except in size. As the 
entire life of the parasite is passed upon the same animal or on another 
animal of the same kind, its range of habit is easily stated. 
But very few of the species are ever found upon any other species of 
animal than that which they normally infest, and if so always upen 
very nearly related species. Whether this is due 
to differences in the thickness of the skin, of tem- (4 
perature, of the size of the hair to which they must 
adhere and to which their feet are adapted, or to 
some subtle difference in the odor or taste peculiar 
to their particular host which leads them to dis- 
card all others, we are unable to say. 
The mouth parts are necessarily capable of great 
extension in order to reach the blood of their 
hosts. Uhler says (Standard Nat. Hist., Vol. II, 
p. 209): “A fleshy unjointed rostrum, capable of 
great extension by being rolled inside out, this 
action serving to bring forward a chaplet of barbs 
which embed themselves in the skin to give a firm 
hold for the penetrating bristles, arranged as 
chitinous strips in a long, slender, flexible tube, 
terminated by four very minute lobes, which probe 
to the capillary vessels of asweat pore. The blood 
being once reached a current is maintained by the 
pulsations of the pumping ventricle and the per- 
istaltic movements of the stomach.” 
The species infesting man are so nearly related 
to the others that we can not well pass them by 
without notice. 
THE CRAB LOUSE. 
(Phthirius inguinalis Leach.) 
If we may depend upon ancient writers, this / 
species has long been a companion of man. <Ac- 2 
cording to Denny it is recorded by Herodotus, and ee setae ‘ - : P 3 
according to Piaget was referred toin the writings — showing rostrum and ex- 
of Aristotle. Some of the ancient accounts treat ra ME shee» 
of it as occurring in the most prodigious numbers ; . 
and causing most serious ailments to the infested parties. The disease 
produced gained the name of Phthiriasis, though doubtless this term 
_ has been applied also to the attacks of the other species of parasites 
infesting man. 
Its attacks are said to be more severe than those of the other forms 
of lice, although it is quite probable that in the worst cases reported the 
