PARASITA 161 



the hairs, and in a few forms there are still other speciaHzed 

 clasping structures to strengthen this hold. In some the 

 antennse serve to help hold on. In one form there is a 

 tubercle developed so that it fits against the pair of legs 

 next forward so that it seems to act as a clasping organ. 

 These suctorial lice are limited to mammals for their hosts. 

 The mouth parts are doubtless adapted to the reaching of 

 the capillary blood system in these hosts and in their life 

 history they show adaptation to the parasitic habit, the eggs 

 being glued to the hairs, the larvae on first hatching being 

 capable of attaching themsehes to the hairs so that the 

 entire life-cycle is distinctly parasitic. Their migrations 

 from these host forms are simply for the purpose of scatter- 

 ing to other individuals of the same species. There is a 

 rather distinct tendency for the individuals to migrate to 

 younger animals of the same species. There is not a very 

 evident series of broods in a year — they probably breed 

 rather promiscuously. They have a constant host and 

 constant warmth. Three species affect man and the horse, 

 ox, sheep, hog, dog, and a great number of other mammals 

 are known to support one or more species. 



Short-nosed Ox Louse (HoBmatojnmis eiirysternns Niizsch). 

 — The short-nosed ox louse is the common species occurring 

 on cattle. The full-grown females are about one-eighth 

 to one-fifth of an inch long, and fully that in width, while 

 the males are a little smaller and proportionately a little 

 narrower. Aside from the difference in size the sexes differ 

 very decidedly in the markings and structural features upon 

 the under side of the body. The female is bluish leaden or 

 gray in color. The males have a broad black stripe rlmning 

 forward from the end of the body to near the middle of the 

 abdomen, as shown in Fig. 117. The females have no 

 indications of this stripe, but the black, broken band of the 

 upper side of the terminal segment extends slightly around 

 on the under side. The most important character, however, 

 is the presence of two little brush-like organs on the next 

 to the last segment, as shown in Fig. 117. 



The head is bluntly rounded in front, nearly as broad as 

 11 



