ITCH-MITE, Aearus scabiei, or Sareoptes scabici. Although the itch was undoubtedly known both to the Greeks and Romans, there is no certain evidence that a mite was recognized as the cause of the disease earlier than by Aven zoar, an Arabian physician of the twelfth cen tury. Throughout the Middle Ages, and till the nineteenth century. the necessary connection be tween the disease and the mite was universally recognized. During the early part of the last century the existence of 'the itch-mite was dis trusted, until in 1S34 Renueei, a Corsican stu dent, demonstrated the existence of the creature.
The itch-mite is now an unusual pest in the United States, and in ordinary hospital practice a case is reported only at long intervals. A cage reported in 1892 by Dr. Robert Hessler. of In dianapolis, attracted much attention. The skin of the patient was estimated to contain 7.000. 000 eggs and 2,000,000 mites. The itch-mites of the lower animals were formerly considered to be distinct from the species affecting human be ings; hut Raillet, the latest authority, believes them to he only varieties, and it scent; there fore that human beings may be infested from certain of the domestic animals. The true human
itch is Aearus seabici, now known as Sareoptes seabici hominis: the Norway itch, Sarroptrg sea biei erustos‘r : that of the horse. Sareoptes sea biei cqui: of the sheep, Rarcoptes seabiei ori•, etc. All stages of the parasite occur on the host, upon which it is absolutely dependent for exist ence.
The adult female mite is considerably larger than the male; it is visible to the naked eye, and forms a roundish, grayish-white corpuscle, not unlike a starch-granule; it is about one-fifth of a line in length, and one-seventh in breadth. When seen under the microscope, it presents a truncated tortoise-like shape, and is seen to be studded with hairs and bristles. The head ter minates in two pairs of mandibles, and these n andibles afford good characteristic distinctions of the species. The males are much scarcer than the females.
Consult: Raillet, Zoologic medical(' (Paris, 1895) : and Osborn. Insects Aff(eting Domestic Animals ( Department of Agriculture, Washing ton, 1896). See ITCH; ACARUS FOLLICt'LORUM.