:!4] 



The abdomen has the following structures: dorsum, ven- 

 tral plate, anal covers, genital covers, often pteromorpha:', and 

 sometimes large bristles. The dorsum of the abdomen consists 

 of a single large chitinous plate. The ventral plate varies 

 much in size; is sometimes confluent with the dorsum, and 

 contains the genital and anal apertures. The genital aperture 

 is anterior to the anal aperture, and is closed by two chitinous 

 '■folding doors", known as the genital covers. The anal aper- 

 ture is similarly closed, its "folding doors" being termed the 

 anal covers. Sometimes on the dorsum, rarely on the ventral 

 plate, long bristles may be found, though frequently the ab- 

 domen is haii'less. In some genera, as /'c/iips and Oriltiifa. there 

 are chitinous wing-like expansions of the abdomen termed 

 pteromorpha' (1'!. XXX 111.. Fig. ^, ptn:). 



The legs (Fig. 5 ) consist of five 

 segments, namely, coxa, femur, 

 genual, tibia, and tarsus. The 

 coxa (Co. ).or basal segment, is 

 usually the shortest and stoutest 

 of the segments, and sometimes 

 has a blade-like expansion ( HI. ] on one side. The femur ( Fp.) 

 is usually the largest and sometimes the longest .segment. The 

 genual [Gc.) is very small and inconspicuous. The til)ia {Ti.) 

 is usually subequal to the tarsus ( 7V/. ). and often bears, espe- 

 cially on the front pair of legs, a long tactile hair at its di.stal 

 end. The tarsus ends in either one ( monodactyle) claw or 

 three (tridactyle) claws, and never in two except in the 

 species Xuflinis (nxnuiii'iisis. 



The parts most used for systematic iiurposes are the 

 pseudostigmatic organs, lamella% translamella. pteromorplue, 

 and ungues. 



Internal Anatomy. 



Most of the internal organs of the oribatids may be divided 

 into three systems: the digestive, tracheal, and i-eproductive 

 sy,stems. The digestive and i-eproductive organs occupy most 

 of the bodv cavitv. 



Fig. 5. (Jrihala innHicDiiKi, le^ 4. 



