102 



EEPOET 108^ U. S. DEPAKTMEXT OF AGEICULTUEE. 



others are found in moss or on damp soil. Berlese has divided the genus into several; 



one of them, Trizetes, appears to be very distinct. Of Hermannia we have several spe- 

 cies, mostly in the north; some have a curious, 

 campanulate process on each side of the body. 

 In recent yeai's Berlese has described many re- 

 markable exotic forms in several new genera. 



Family HOPLODERMATIDJE. 



The Hoplodermatidae are separated from the 

 genuine Oribatidse in having the cephalothoi-ax 

 movably attached to the abdomen. By this 

 means the animal is able to roll up, concealing 

 the legs. The legs of the Hoplodermatidae are 

 attached to the body close together, and the 

 whole sternal stnicture is soft and membranous, 

 instead of coriaceous, as in the Oribatidae. 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 aper- 

 tures. Phthiracarus glabrata Say is one of our 

 largest and most common forms, and is found 

 on moist ground. The species of Hoploderma 

 are most common in decaying wood or moss. 

 T^Tien disturbed they roll up, "play possum," 

 and are then not easily discerned. One of the 

 species described by Riley was supposed to 

 feed on the Phylloxera, but such is not the 

 case, its food eA-idently being decayed vege- 

 table matter. The young occur in the same localities as the adults. The nymph 

 is a soft, yellowish -wliite creature, not unlike a Tyroghjphus. Tliey have long man- 

 dibles, and can not fold up like their parents. Our forms have been described in 



Fig. 20S. — HypochtJwnius texanus. 

 (Original.) 



Fig. 209.— Hoploderma sphacrula. (Author's ^^^- '2l0.-rhtiitracarus sp., 



illustration.) closed up; ventral view. 



(Author's illustration.) 



Hoploderma (Iloplophora) and Phthiracarns (Trilia) (fig. 210), but various other genera 

 are known; the principal ones may be grouped as below: 



1. Posterior part of abdomen segmontod; one claw to each tai-sus Protoplophora. 



Posterior part of abdomen not segmented 2 



2. Ventral apcrturcis distinctly sej)araled; ventral area rather large Mcsoplophora. 



Ventral apertures nearly or quite contiguous 3 



