. The Acarina or mites. A review of the group for the use of economic entomologists. Mites. 58 REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. the tip of the hody, while in other species there is a ciir\'ed groove in front of the anus. and reaching back each side toward the margin of the body. In all forms there is a lateral groove on each side reaching forward to the genital pore. In the males of several genera there are one or two corneous, triangular plates, known as the anal plates, each side of the anus. Sometimes the abdomen terminates in a short median process or tail. The legs arise on ea
. The Acarina or mites. A review of the group for the use of economic entomologists. Mites. 58 REPORT 108, U. S. DEPARTMENT OF AGRICULTURE. the tip of the hody, while in other species there is a ciir\'ed groove in front of the anus. and reaching back each side toward the margin of the body. In all forms there is a lateral groove on each side reaching forward to the genital pore. In the males of several genera there are one or two corneous, triangular plates, known as the anal plates, each side of the anus. Sometimes the abdomen terminates in a short median process or tail. The legs arise on each side on the anterior part of ihe venter. The cox?e are sometimes close together, some- times more widely separate. The legs are usually slender, subequal in length, but the foiu-th pair is rather the longest, and sometimes larger than the others. Each is composed of at least six joints, as follows, from base outward; coxa, trochanter, femur, tibia, metatarsus, and tarsus. The latter is commonly more or less definitely divided into two parts. At the tip of the tarsus is a pair of large claws (fig. 112) situated on a rather long pedicel, and between them is a pulA-illus. On the upper surface of tarsus I is a pit covered by a membrane; this is known as Haller's organ, in honor of its discoverer, and is supposed to be an organ of audition, but more probably to recognize the approach of a host. One or more of the coxae are armed behind by spinelike processes or teeth. In the males of some species the hind coxae are greatly enlarged. Above and usually slightly behind the hind coxae are the stigmal plates (fig. 108), containing near their centers the stigmal orifices or spiracles. Each plate is a corneous piece, the surface of which is marked by granules of smaller or larger size. The shape and sculpture of the stigmal plate is quite constant in each species, but differs in the Fig. 107. — Hypostome and mandibles of a tick. (Origi- nal.). Please note that these images are
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