ORDER TRACHEARI^. 505 



AcARUS, Fah., Latr. Sarcoptes, Latr., 



Having, as well as the pi'eceding, two didactylous antenna3- 

 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, Ricinio}, Lat.), have also eight feet 

 exclusively proper for running, but are without antennae-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., Fah. SciRUS, 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., Scirus 

 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 j 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 arc scarcely 



