70 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXVIII. 



ably are slightly beneficial. There are doubtless 200 species of this 

 family in the I'nited States, but only about fifty or sixty, mainly from 



Fig. 13.5.— Gymn'ob.\tes glabek. 



Fiii. 134.— Oribata .minvta. 



the Eastern States, have been clescril)ed. On 

 account of their minute size, obscure hal)its, 

 and small economic value they are not faxorites 

 with collectors. 



The superfamily Oriliatoidea includes two 

 well-marked famili(>s. One, the Hoi)loder- 

 mida\ are separated from the genuine Oriba- 



tida' in having the cephalothorax moval)ly attached to the abdomen. 

 By this means the animal is a])le to roll up, concealing the legs. The 

 legs of the Hoplodcrmidiv are attached to tiie l)ody, close together, 



and the whol" sternal structui'e is soft and 

 membranous, instead of coriaceous as in 

 the Oribatida\ The palpi are four-jointed. 

 The dorsal plate of the abdomen extends 

 down upon the sides, so that the venter is 

 very narrow and almost wholly occupied 

 by the large genital and anal apertures. 

 We have two genera of this family — IIoj)- 

 hnh-riixt, with one claw to tarsus, and 

 PltfJi/fdnirvs, with three claws to tarsus, 

 and a narrower venter. We have a few 

 species in each genus: ]*hf1t!nicarns (jJa- 

 lyiuitd Say is one of our largest and most 

 common foi-ms. and is found on moist 

 ground. The species of Iloplodci'iiui are 

 most common in decaying wood or mo.ss. 

 When disturbed they roll up, play "pos- 

 sum,'' and are then not easily discerned. One of the species described 

 ])y Doctor Kiley was supposed to feed on the Phylloxera, but such is 

 not the case. 



Fig. 136.- Oiui'dHA elongata (i'ku 



GA.NDE). 



