. The Acarina or mites. A review of the group for the use of economic entomologists. Mites. 10 REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. minated by from one to three claws or ungues. In some groups there is a difference in this respect between the young and the adult, and frequently one or more pairs of legs are destitute of claws. The claws are not often toothed. In many cases there is a median cup-shaped sucker, pulvillus, caroncle, or ambulacrum between the claws or bearing them. The reproductive organs, as in other arachnids, open on the ventral surface of the abdomen near the base. The
. The Acarina or mites. A review of the group for the use of economic entomologists. Mites. 10 REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. minated by from one to three claws or ungues. In some groups there is a difference in this respect between the young and the adult, and frequently one or more pairs of legs are destitute of claws. The claws are not often toothed. In many cases there is a median cup-shaped sucker, pulvillus, caroncle, or ambulacrum between the claws or bearing them. The reproductive organs, as in other arachnids, open on the ventral surface of the abdomen near the base. The female aperture (vulva or epigynum) is of various shapes and sometimes closed by flaps or folding doors. The male apertiu-e (epian- drum) is usually smaller than that of the female. The body is often provided with hairs, bristles, or scales, which are of characteristic nature and arrangement in each species. In many of the soft-bodied forms there are chitinous plates, scutae, or sliields, sometimes so large or so numerous as almost completely to cover the mite. These. Fig. 4.—Legs of various mites. (Author's illustration.) shields are often sculptured or pitted in a characteristic manner. Frequently there are secondary sexual differences both of color and structure, as will be noticed under each family. The male is often a little smaller than the female, but in many cases there is no apparent difference in size. The internal anatomy (fig. 5) of mites is marked by great centralization of parts, the various organs being much more crowded together than with other arachnids. The alimentary canal when fully developed consists of the pharjTix or sucking organ; the oesophagus; the stomach or ventriculus, with its coeca; the hind gut or intestine, and the Malpighian vessels, which enter the latter near the rectum. The pharynx is a partially chitinous tube, convex below, concave above; to its upper part or roof are attached the muscles which, upon contracting, elevate the roof. A ser
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