MITE (AS. mite, OHG. miza, miz.:11, Ger. Miele; probably connected with Goth. maitan, OHG. smvsrnn, to cut). Any one of the Acarina, an order in the class Arachnida. They may be distinguished from other arachnids by their small size; by the unse,Lmiented holy, without a constriction between the anterior portion or cephalothorax and the posterior portion or ab domen; and by the lack of median eyes. There are exceptions, however. to all these characteris tics, and certain forms have been misplaced even by naturalists. The month-segments have become united to form a beak or rostrum, but this char acter is not easily recognized. The young mite, on hatching from the egg, is not provided with eight legs as are other arachnids, but with only four or six, except in the case of Pteroptus. In size mites vary from tiny creatures, invisible to the naked eye, to certain tropical forms fully half an inch long.
Typically, mites have four pairs of legs, ar ranged more or less definitely in two groups. The two hinder pairs are apparently attached to the abdomen, while the anterior pairs are close to the mouth-parts, which consist of mandibles of varied elmracter, palpi, and The man dibles are typically chelate, but in several fami lies they are reduced to needle-like piercing organs. In the ease of certain gamasid mites the mandibles are nearly as long as the entire animal, and can be wholly retracted within the body, or suddenly extruded to seize the prey. The palpi are of for kinds. Simple, (inform palpi, which have a tactile function, are found in many fami lies. In some parasitic forms the palpi are re duced in size and united to the rostrum. In many predatory mites the palpi are modified for raptorial orgam. In some of the water mites the palpi have become organs for holding the mite to other objects. The legs of mites are composed of from five to seven segments, and commonly terminate in from one to three claws. In many genera a eup-shaped sucking-disk or ambulaerum is attached to the tarsus or last segment. The reproductive organs, as in other arachnids, open on the under side of the abdo men near its base. The body and legs are more or less thickly clothed with bristles, hairs, or Scales, which are of characteristic nature and arrangement in each species. In many of the
soft-bodied species there are chitinous plates or shields, sometimes so large or numerous as al most completely to cover the mite. In the ticks the body is flat, and of a tough, leathery con sistency.
The sense organs are few and of simple nature. mites have no eyes, but in some there are (2ne or two oeelli-like spots on each side of the cephalothorax. A few families have what are considered organs of hearing. With the ticks this organ is a membrane-covered pit in the anterior tarsi; in the beetle-mites it is a pore on the posterior margin of the cephalothorax, from Nv bielt arises a bristle. The sense of touch is supposed to reside in some of the hairs of the body or legs. In many mites there is a consider able difference in appearance between the two sexes. although there is not often much differ ence ill size.
is the peculiar characteristic of the anatomy of mites. 'lie various organs are more crowded together than in other arachnids. The digestive system, when complete, consists of the pharynx, or sucking-organ. the esophagus, the ventricmlus or stomach, with its ewea, the hind gut, and the iNlalpighian vessels. The (esophagus is a long, simple tube extending through the centre of the brain. The stomach is of varied size, ac cording to food-habits; in some forms it is very small, while the ca-ea are numerous and long. The hindgut or intestine is a short tube ending in the rectum. The Malpighian vessels, when present. are two in number, and enter the intes tine near its end. In some mites there is a well developed dorsal pulsating organ or heart, but in others it is not present. The nervous system consists of one ganglionic mass surrounding the esophagus, from which all the principal nerves arise. .lany mites have an elaborate system of traelic.e by which they breathe and which open in various parts of the body, in many common species near the mandibles, but in the ticks and gamasids they open by stigmata near the hind legs. A great number of mites, however, have no internal respiratory system whatever. In these the skin is soft and they absorb oxygen by osmosiS.