504 CLASS ARACHNIDA. 



Gamasus, Latr., Fah. 



The forceps are didactylous, and the palpi projectingj or very 

 distinct, and in the form of a thread. 



Some have the upper part of the body clothed, altogether 

 or in part, with a scaly skin ; others have the body entirely 

 soft. Some species of this division live on different birds and 

 quadrupeds ; some are known, such, especially, as the acarus 

 telarius of Linnasus, which form on the leaves of several vege- 

 tables, particularly on those of the elm, very fine webs, and 

 injure these plants very much. This species is reddish, with 

 a blackish spot on each side of the abdomen. 



Cheyletus, Latr., 



Which have also didactylous forceps, but the palpi are thick, 

 in the form of an arm, and terminated like a scythe. 



Oribata, Lat. Notaspis, Hermn. 



The forceps are again didactylous, but the palpi are very 

 short, or concealed. The body is covered with a firm coria- 

 ceous or scaly skin, in the form of a buckler or shield, and the 

 feet are either long or of middle size. 



The fore-part of the body is advanced like a muzzle. We 

 often see an appearance of corslet. The end of the tarsus is 

 terminated by a single hook in some, by two or three in the 

 others, without vesicular cushion. 



They are found on stones, trees, and moss, and walk slowly. 



Uropoda, Latr., 



Which have, as analogy would lead us to presume, the forceps 

 pincer-like. The palpi are not apparent or projecting. The 

 body is entirely covered with a scaly skin, but the feet are 

 very short, and there is a thread at the anus, by means of which 

 they fix themselves on the body of some coleopterous insects, 

 and suspend themselves in the air. 



