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Show 214 ARACIINIDES. Sino, Lat. Projecting ch~licerre nearly as long as the body; eyes separated and placed on different insulated tubercles( 1 ). MAcROCIIELEs, Lat. Extremely salient and very long chelicerre; but the eyes null or sessile; the two anterior legs very long and antenniform; the top of the body forming a plate or scale without distinct annuli. To this genus I refer the .!lcarus marginatus and the .IJ.c. testudi· narius, of Hermann, Jun., Mem. Apter., p. 76, pl. vi, fig. 6, and p. so, pl. ix, fig. 1. TROGULus, Lat. Anterior extremity of the body projecting like a clypeus, and re· ceiving the chelicerre and other parts of the mouth into an inferior cavity. The body is flat and covered with a very firm skin(2). In the second tribe of the Holetra, that of the AcARIDEs, we sometimes find chelicerre, but they are simply formed of a single forceps, either didactyle or monodactyle, and are hidden in a sternal lip; sometimes there is a sucker formed of united lancets; or finally the mouth consists of a simple cavity without any apparent appendages. This tribe is composed of the genus · AcARus, Lin. Most of these animals are very small or nearly microscopical. They are observed everywhere. Some of them are errant, and of these some are found under stones, leaves, the bark of trees, in the earth, in water, dried meat, old cheese, and putrescent ani· mal matters. Others are parasitical, living on the skin or in the fle.sh ~f various animals, which they often, by their excessive multi· phcatwn, reduce to a state of great debility. The origin of certain (I) Sirorubens, Lat., Gener. Crust. etlnscct., ~vi, 2;-.ll.cm·uscrassipCB, Herro, Mem. Apter., ITI, 6, and lX, Q. N. . <2). Troglllus nepteformis, Lat. Gener. Crust. and Insect., I, vi, 1; Pltalangium frtrm·matum, L.-South of France, Spain. THACIIEAUIJF .. 215 , 5 such as tho itch, is attributed to particular species. The d1sease ' . . ·ments of Dr Galet prove that 1f the Acar1 of the human psora experJ J.> • • 1 ced on the body of a per1ectly healthy person, they w1ll mocu-be ph~m with the virus of that disorder. Various species of Acari late I ISO found on Insects, and some of the Coleoptera that feed on ca-are a f . . daverous or excrementitious substances are requently covered w1th h They have even been observed in the brain and eye of Man. t em. The Acari, or Mites as they are vulgarly termed, are oviparous, d excessively prolific. Several of them at first have but six legs, athne remaining two being developed shortly a f ter. 'fh e1· r tars1· ter-minate in various ways according to their habits. Some-AoARIDES, Lat.-or the Acari proper, have eight legs, solely destined for walking, and chelicerre. TnoMBIDIUM, Fab. The chelicerre monodactyle, or terminated by a movable hook; salient palpi, pointed at the end, with a movable appendage or species of finger under their extremity; two eyes, each placed on a little immovable pedicle. The body is divided into two parts, the first ofwhich, or the anterior, is very small, and bears the two first pair oflegs, together with the eyes and mouth. Tromb. lwlosericeum, Fab.; Herm., Mem. Apter., pl. I, 2, and II, 1. Very common in gardens in the spring; blood-red; abdomen nearly square, posteriorly narrowed, with an emargination; the back loaded with papillre, hairy at base, and globular at the extremity. · Tromb. tinctorium, Fab.; Herm. Apter., I, 1. Three or four times the size of the preceding; it furnishes a red dye. The East Indies( 1 ). EnYTHRJEus, Lat. The chelicerre and palpi of Trombidium; but the eyes are not placed on pedicles, neither is the body divided(2). GAMAsus, Lat. Fab. Didactyle chelicerre; yery distinct or proje~ting filiform palpi. The superior surface of the body, in some, is either wholly or partially invested with a scaly skin(3). {1) T. fuliginosum, Hcrm. Mem. Apt. I, 3;-T. bicolor, lb. II, 2;-T. asaimile, lb., 3; T. curtipes, lb., 4;-T. triganum, Ib., 5;-T. trimaculatum, Ib., 6 . (2) Erytltrmus pltalang£oides, Lat.; Trombidium phalangioides, Herm.: lb., .'' 10;-1'rombidium quisquiliarum, lb., 9;-Tromb. parietinum, lb., 12;-T. pu:nl· fum, lb., ll, 4;-T. murorum, lb., 5. (3) Gamasus marginatua, Lat.: Jlcarus marginatua, Herro., Mem. Apter., VI, 6, |
