504 
CLASS ARACHNIDA. 
Gam asus, Latr ., Fab . 
The forceps are didactylous, and the palpi projecting, 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 Linnaeus, 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. 
