288 ENTOMOLOGY FOR MEDICAL OFFICERS 



The disease known as Japanese River Fever has been said 

 to be due to the attack of some larval Acarine of this or 

 some allied family. 



Family Sarcoptid^ : Itch- and Scab-mites. 

 (Gr. o-a/o^= flesh ; /coTTTeii' = to pierce.) 



This is a notorious family of minute parasitic mites, most 

 of which live on mammals and birds, sometimes merely 

 attaching themselves to the hairs or feathers, but often 

 burrowing into the epidermis and causing eczematous 

 affections such as itch, mange, and scab. 



The body is generally squat-ovate, though sometimes of 

 fantastic shape, and shows no division of cephalothorax and 

 abdomen ; anteriorly there is a rostrum formed chiefly by the 

 chelicerae, which usually are chelate, and the short, 3-seg^ 

 mented, more or less adherent pedipalps ; posteriorly in the 

 male there are usually suckers. The cuticle is soft, finely 

 striated transversely, and is produced at definite points into 

 long stiff bristles, or coarse spinules. The legs, which are 

 attached ventrally by chitinous supporting-rods, are stumpy 

 and are arranged in two sets, two pairs being placed near the 

 rostrum and two pairs near the hinder end of the body ; the 

 tarsi, or some of them, generally end in a sucker. 



Of the five subfamilies into which the group is sub- 

 divided the most important from the medical standpoint is 

 that of the Sarcoptince, or common itch- and mange-mites. 

 The species of this subfamily attack the epidermis of man 

 and the epidermic structures of mammals and birds. Their 

 body is round or broadly ovate, their cuticle is transversely 

 striated, and some of their legs end in a long-stalked sucker. 

 In the common itch-mite of man, Sarcoptes scabiei, the male 

 is only about h^lf the size of the female, and has suckers on 

 all the legs except the third pair, the female having them 

 only on the first two pairs ; the third pair of legs of the male, 

 and the third and fourth pairs of the female, end in a long 

 bristle. The female burrows down as far as the juicy 

 Malpighian layer, depositing a row of eggs as she goes, and 

 ultimately dies at the end of the burrow. The eggs hatch 

 in a few days, and the young are pushed up to the surface, 



