TRACHEARI^. 82>1 



Insects, and some of the Coleoptera that feed on cadaverous or excre- 

 mentitious substances arc frequently covered with them. They have 

 even been observed in the brain and eye of man. 



The Acari, or Mites as they are vulgarly termed, are oviparous, 

 and excessively prolific. Several of them at first have but six legs, 

 the remaining two being developed shortly after. Their tarsi ter- 

 minate in various ways according to their habits. 



Some — AcARiDEs, Lat. — or the Acari proper, have eight legs, 

 solely destined for walking, and chelicerae. 



Trombidium, Fab. 



The chelicerae menodactyle, or terminated by a movable hook ; 

 salient palpi, pointed at the end, with a moveable appendage or spe- 

 cies of finger under their extremity; two eyes, each placed on a 

 little immoveable pedicle. The body is divided into two parts, the 

 first of which, or the anterior, is very small, and bears the two first 

 pair of legs, together with the eyes and mouth. 



Tromb. holosericeum,Fs.h.; Herm., Mem. Apter., pi. 1,2, and 

 II, I. Very common in gardens in the spring ; blood-red; ab- 

 domen nearly square, posteriorly narrowed, with an emargina- 

 tion; the back loaded with papillae, hairy at base, and globular 

 at the extremity. 



Tromb. tinctorium. Yah.; Herm. Apter.; 1,1. Three or four 

 times the size of the preceding ; it furnishes a red dye. The 

 East Indies *. 



Erythr^us, Lat. 



The chelicerse and palpi of Trombidium; but the eyes are not 

 placed on pedicles, neither is the body divided f . 



Gamasus, Lat. Fab. 



Didactyle chelicerae; verj' distinct or projecting filiform palpi. 

 The superior surface of the body, in some, is either wholly or 

 partially invested with a scaly skin |. 



The body is entirely soft in the remainder. Several species of 

 this division live on Birds and Quadrupeds. Some are known ; 

 such as the 



Gam. telarius ; Ac. telarius. Fab .; which form extremely fine 

 webs on the leaves of several plants, particularly of the Elm, and 



* T. fuliginosum, Herm. Mem, Apt. I, 3 ; — T. bicolor, lb. II, 2 ; — T. assimile, 

 lb., 3 ,• T. curtipes, lb., 4; — T. trigonum, lb. 5 ; — T. trimaculatum, lb., 6. 



-f- Erythraus phalangioides, Lat.; Trombidium phalangioides, Herm., lb., I, 10; 

 — Trombidium quisquilliarum, lb., 9; — Tromb. parietinum, lb., 12 ; — T. pusillum, 

 lb., 11,4 ; — T. murorum, lb., 5. 



X Gamasus marginatus, Lat. ; Acams marginatus, Herm., Mem. Apter., VI, 6, found 

 on the corpus callosum of the human brain; — Trombidium longipes, Herm., lb., 1, 

 8; — Acanis coleoptratorum, Fab.; De Geer, Mem. Insect., VII, vi, 5 ; — Acarus 

 hirundinis, Herm., lb., I, 13 ; — Ac. vespertilionis, lb. 14 ; Trombidium bipustulatum, lb., 

 II, 10; — Tromb. socium, lb., II, 13; — Tromb. tiliarium, lb., 12; — Tromb. telarium, 

 lb., 15 : these three species live in society on leaves, covering them with extremely 

 fine and silky filaments; — Tromb. celer, lb., 14 ; — Acarus gallince, De Geer, Insect, 

 VII, vi, 13. 



VOL, in. Y 



