96 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



Tlie mandibles are chelate^' and vary in leng-th with the genus. The 

 ventral openings are in the usual position, and in the male there is 

 often a pair of copulatory suckers near the tip. There are frequently 

 sexual ditferenees; some mal(>s have the third pair of legs very large 

 and long, while the fourth pair is very small. Sometimes there are 

 plate-like lobes at the tip of male abdomen, and the tarsi may termi- 

 nate dift'erentiy in the two sexes. The 8arcoptid;e live in the skin of 

 mammals, including man and a few ))irds. The female burrows into 

 the skin, depositing i'gg^ on the way. The young, on hatching, start 

 l)urrows of their owmi, so that a host is infested in patches. These 

 burrows or cuniculi are close to the surface, and sometimes result in 

 lo()S(Miing pieces of the epidermis so as to produce a scaly effect or 



Fin. Is2. — Sakcopti 



IKIMINIS, FKMAI.E. 



Fk;. Is;;. — Lei; of a Sarcoptes. 



crust. Frecpiently there are vesicles, papules or pustules, which may 

 become ulcerated by scratching. The different species produce dif- 

 ferent effects, and even the same species when on different animals. 

 "When upon a hairy animal, the hair usually falls out in the affected 

 portions. The young Sarcojdes^ when newly hatched, has ])ut three 

 pairs of legs; the last ending in a long bristle; and there are no chiti- 

 nous bands. Some species moult four times ))efore maturity. When 

 adult they i>air, and the female wanders a little in search of a good 

 burrowing j^lace. At this time the mites can exist for a long period 

 if removed from their hosts and kept in a moist situation; but if 

 exposed to dryness, they soon die. The burrow is made l)v eating 



«Furstenberg in his great work, Die Kriitzemilben der 3Iens!chen, figures two 

 pairs of chelate mandibles; this is a manifest error, and weakens one's faith in his 

 fine figures. 



