Bugs, Cicadas, Aphids, and Scale-insects 
217 
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 a sweat-pore.” Of the three species of 
Pediculus infesting unclean persons, P. capitus (Fig. 299), the head-louse, 
is longer than wide, whitish with faint dark markings at the sides of the 
thorax and abdomen; P. vestimenti (Fig. 300), the body-louse, is of the 
same shape and general appearance, but when full grown has the 
dorsal surface marked with dark transverse bands; while P. inguinalis 
(Fig. 301), the crab-louse, has the body as wide as long, with strong 
legs spreading out laterally so as to increase the apparent width very 
Fig. 301.—The crab-louse of man, Phthirius inguinalis. (After Lugger; much enlarged.) 
Fig. 302.—Egg of crab-louse, Phthirius inguinalis. (After Lugger; much enlarged.) 
Fig. 303.—Sucking dog-louse, Hamatopinus piliferus Burm. (After Lugger; natural 
size indicated by line.) 
much. The eggs (Fig. 302), called “nits,” of these lice are whitish and are 
glued to the hairs (in the case of P. capitus) or deposited in folds of the 
clothing (P. vestimenti) , and the young, when hatched, resemble the parents 
except in size. The whole life is passed on the body of the host. The prime 
remedy for these disgusting pests is cleanliness. Various sulphur and mercu¬ 
rial ointments will kill the insects. 
The lice of the domestic animals belong to a different genus, Haema- 
topinus, but are very similar in appearance and structure to the head-lice 
of man. H. piliferus (Fig. 303), of dogs, is about X V inch long, reddish 
yellow, and with the abdomen thickly covered with fine hairs and minute 
tubercles; H. eurysternus (Fig. 304), the short-nosed ox-louse, of cattle, 
is from £ inch to } inch long, fully half as wide, with the head bluntly 
rounded in front and nearly as broad as long; H. vituli , long-nosed ox-louse, 
