ORDER TRACHEARUE. 
505 
Acarus, Fab., Lair. Sarcoptes, Latr ., 
Having, as well as the preceding, two didactylous antennce- 
pincers, palpi very short or concealed, but the body very soft, 
or without scaly crust. 
The tarsi have at their extremity a vesicular pellet. Many 
species feed on our alimentary substances ; others are found 
in the ulcers of the human itch, in those of the horse, dog, 
and cat. 
Other mites (the Tics, Ricmicc , Lat.), have also eight feet 
exclusively proper for running, but are without antennoc-pin- 
cers or forceps properly so called. These organs are replaced 
by two laminae, like lancets, forming, with the tongue, a 
sucker. 
Sometimes they have distinct eyes, projecting palpi, fili- 
form, and free ; a sucker composed of membranaceous pieces, 
and without denticulations ; and the body very soft. They 
are erratic. 
Bdella, Latr., Fab. Scire s, Hermn 
Which have elongated palpi, elbowed with threads or hairs at 
the end ; four eyes; and the hinder feet the longest. Their 
sucker is advanced in the form of a conical bill, or like an 
awl. They are found under stones, the barks of trees, or in 
moss. 
Acarus longicornis , Lin., La Pince rouge , Geoffr., Seims 
vulgaris , Hermn. Mem. Apt. iii. 9 ; ix. Scarcely half a 
line in length, of a scarlet-red, with the feet paler ; sucker in 
the form of an elongated and pointed bill; palpi, with four arti- 
culations, the first and last of which are the longest ; the last 
is a little shorter than the first, and terminated by two threads. 
Common in the environs of Paris, under stones. 
Smaridia 
Are distinguished from Bdella by the palpi, which are scarcely 
