ORDER TRACHEARI^. 503 



that of the itch. It appears to result from the experiments of 

 Dr. Gales, that the mites of the human itch, placed upon the 

 body of a sound person, will inoculate him with the virus of 

 this maladj. We also find various sorts of mites on insects, 

 and many coleoptera which live on cadaverous or excremen- 

 titious substances, are sometimes altogether covered by them. 

 They have been observed even in the brain and the eyes of man. 



The mites are oviparous, and multiply exceedingly. Many 

 are born with only six feet, and the other two are developed a 

 little time after. Their tarsi are terminated in various ways, 

 and appropriate to their habits. 



Some (Ac A RIDES proper) have eight feet, exclusively 

 adapted for running, and forcejDS. 



Trombidium, Fah., 



Which have the forceps talon-like, or terminated by a mobile 

 hook; projecting palpi, pointed at the end, with a mobile 

 appendage, or sort of claw, under their extremity ; two eyes, 

 situated each at the end of a small fixed pedicle, and the 

 body divided into two parts, of which the first or anterior is 

 very small, and carries, besides the eyes and mouth, the first 

 two pair of feet. 



T. Iiolosei'iceum, Fab., Hermn., Mem. Apt. pi. i. 2. and ii. 

 1. Very common in spring in gardens ; of a blood-red ; the 

 abdomen almost square, narrowed behind, with an emargina- 

 tion ; the back charged with papillae, hairy at their base, and 

 globular at their extremity. 



Another species is found in the East Indies, three or four 

 times larger, and which yields a red tincture. {T. tinctorium, 

 Fab.) Herm. Mem. Apt. I. i. 4. 



Erythrjeus, Latr., 



Which have the forceps and palpi of Tromhidium, but the 

 eyes are not carried on a pedicle, and the body is not divided. 



