216 ARACHNIDES. 



The body is entirely soft in the remainder. Several species of 

 this division live on Birds and Quadrupeds. Some are known; 

 such as the 



Gam. tclarius; Jic. telarius, Fab.; which form extremely fine 

 webs on the leaves of several plants, particularly of the Elm, and 

 are very injurious to them. This particular species is reddish, 

 with a blackish spot on each side of the abdomen. 



Cheyletus, Lat. 

 Didactyle chelicerse; but the palpi are thick, resemble arms, and 

 have a falciform termination(l). 



Oribata, Lat. N'otaspis, Herm. 



The chelicerae are also didactyle in the Oribatse, but their palpi 

 are very short or concealed; their body is invested by a firm, cori- 

 aceous or scaly skin resembling a shield, and their legs are long 

 or moderate. 



The anterior part of the body projects into a snout, and an ap- 

 pearance of a thorax is often observable. The tarsi, in some, are 

 terminated by a single hook, and in others by two or three, without 

 any vesicular pellet. 



They are found on stones, trees, and in moss; their gait is slo\v(2). 



Uropoda, Lat. 



Judging from analogy, we presume that the Uropodse are fur- 

 nished with forceps-like chelicerse. Their palpi are not apparent; 

 their body, still covered with a scaly skin, has but very short legs, 

 and a filament at the anus, by means of which they attach them- 

 selves to certain coleopterous Insects, suspending themselves in the 

 air(3). 



found on the corpus callosum of the human brain; Trombidium longipes, Herm., 

 lb., I, 8; Acarus coleoptratorum , Fab.; De Geer, Mem. Insect., VII, vi, 5; Acarus 

 hirundinis, Herm., lb., I, 13; Ac. vespertilionis, lb., 14; Trombidium bipustula- 

 tum, lb., II, 10; Tromb. socium, lb., II, 13; Tromb. tiliarium, lb., 12; Tromb. 

 lelarium, lb., 15 : these three species live in society on leaves, covering 1 them with 

 extremely fine and silky filaments; Tromb. cekr, lb., 14; Acurus gallinse, De 

 Geer, Insect., VII, vi, 13. 



(1) Acarus eruditus, Schrank., Enum. Insect. Aust., No. 1058, Tab. II, 1; ejusd., 

 peciculus musculi, lb., No. 1024, I, 5. 



(2) See Hermann, Mem. Apter., genus Notaspis; and Olivier, Encyc. Method., 

 Insect., article Oribate. 



(3) Acarus vegetans, De Geer, Insect., VII, vii, 15. The Acarus spinitarsus, 

 Herm. Mem. Apter. VI, vi, 5, perhaps forms a genus intermediate between this 

 and the preceding one. 



