NO. 1382. 



THE ACARINA OR MITES— BANKS. 



51 



uiiile, or of both sexes, is situate in the middle of the sternal plate. 

 The anal opening- is small and placed near the tip of the venter; it 

 is often surrounded l)y a plate. There is a spiracle or breathing- 

 pore on each side of the ])ody, above and slightly in front of the 



fourth coxa. It is surrounded })y a chiti- 

 neus ring, the peritreme, which usually 

 extends forward for a long distance, often 

 in a slightly sinuous line. The legs are of 

 six joints — coxa, trochanter, fenuir, pateUa, 

 and tibia, of subequal length, and a long 

 tapei'ing tarsus. In some species there are 

 indications of a division of the tarsus. The 

 tarsi terminate in two claws, and sometimes 

 a sucker or ambulacrum. In several forms 

 the anterior legs are destitute of claws, and 

 seem to act more as antenna?. In man}^ spe- 

 cies the males have the second pair of legs 

 enlarged and provided with teeth and projec- 

 tions, and sometimes the hind legs are also 

 armed. These legs are used to hold the 

 Female during pairing. 

 The mternal anatomy of the (jamasida^ has 

 betMi studied perhaps more than that of any other family. It difl'ers 

 in various ways from what may be called the typical acarid anatomy. 

 Kramer has shown that in some forms there is a tendinous framework 

 in the middle of the body, a sort of internal skeleton, to which are 

 attached many of tlie larger muscles. . The male sexual organs are 

 usually on the conuuon plan. There is, how- 

 ever, a large accessory gland lying l)etween 

 and beneath the vas deferens. There is no 

 introniittent organ; and sometimes there are 

 two testes. The female generative organs 

 usually differ much from that in other fami- 

 lies. Often there is a semiglobular or botry- 

 oidal ovar\', opening into one (sometimes 

 two) oviducts, that lead to the vagina; a))ove 

 the vagina is a domed chaml)er, the speriua- 

 theca. At times there are two small glands 

 that open into the vagina. In many forms 

 .there is no spermatheca, in which case Michael 

 has discovered the existence of other organs of a most curious nature. 

 Attached to the top of the ovary are two rather clavate arms, known 

 as the lyrate organs; and above is a large sac, the xnccuhis fd'hiineiis^ 

 connected at one end to the ovary and at the other by two amnilate 

 tubes to the acetabula of the coxte of the third pair of h^gs. After 



89. — VENTKK UK PTEROPTUS. 



