THE ACAEINA OR MITES. 



127 



tliree-ioiiited. The mandibles are commonly chelate, but very small. The genital 

 aperture is situate between the third and fourth coxae, and the anus at the tip of 

 the body. The males, which are usually of a different shape than the females, 

 have a pair of copulatory suckers near the tip of the venter. 



These mites feed on the hairs of small mammals, 

 and each genus has some special apparatus where- 

 with to hold onto the hair. In Listrophorus tHe 

 under lip is expanded on each side into a flexible 

 plate which curls around the hair. They occur on 

 rabbits, squirrels, and mice. In Myocoptes (fig. 

 262) the hind pairs of legs are enlarged, the apical 

 joints pro\T.ded with a few large spurs, and these 

 joints can fold back on the basal joints, as a 

 knife blade. By this arrangement they cling to the 

 hair of mice. In Trichoecius the liind tarsal joint 

 is flattened, curved, and pro\T.ded with a spine, 

 which enables the mite to grasp the hair of mice. 

 In Labidocarpus, which occiu-s on bats, the anterior 

 legs are very short and the last joint enlarged and 

 concave below; by these they clasp hairs. The hind 

 legs are normal. Schizocarpus has a similar arrange- 

 ment; it occurs on the beaver. In Chirodiscus the 

 anterior legs have the apical joints flattened and 

 curled, but destitute of claws and sucker. 



Each species is restricted to one or two hosts, as 

 the clasping apparatus is fitted to hold a hair of a 

 certain diameter and can not hold to hairs much 

 smaller or greatly larger than those of its normal 

 host. Little is known regarding their life history. In Labidocarpus the male mates 

 with a n^Tnphal female (as in the true Analgesidse), which molts, and the true female 

 issues only to deposit eggs. Some species of Listrophorus are preyed upon by species 

 of Cheyletus that use the rabbit's fur as a hunting forest. 



This family is based on the pilicolous habit and the possession of some apparatus 

 for use in clinging to the hair. Since tliis apparatus is very different in the ^•arious 



Fig. 261. — Schizocarpusmingaudi: Male 

 and female together. (Author's illus- 

 tration.) 



Fig. 2<S2.— ^[yocoptcs clinging to a hair. (Original.) 



genera it has been siu-mised that the family is not a natural one, but includes forms 

 really belonging to the Analgesidse, T\Togl\'phidae, and Sarcoptidoe. 



The American forms, with the exception of Schizocarpus mingaudi Trouess. (figs. 260, 

 261) on the beaver, Listrophorus validus Banks (fig. 263) on the muskrat, and L. gibbus 

 Pagenst. on the rabbit, have not been investigated The former species is, however, 

 very peculiar in many ways. The male has the third pair of legs large, the fourth 

 very small, and mates with a nymphal female, which possesses but one pair of legs. 

 The adult female is of normal appearance. It has been taken in Texas, California, 

 and Washington, and also occurs in Europe. 

 S8S54°— 15- 9 



