ACABUS, the tick or mite, in natural history, so called, because it is deemed so small that it cannot be cut, is a genus of insects belonging to tlte ortler of Aptcra, in the Linnwan system. Gmelin, in the last edition of Linna:us's system, has elghty-two species ; of which, some are inhabitants of the earth, others of water sonic live on trues and plants, other; among stones, and others on the bodies of other animals, and even tinder their skin. The generic character is, lei.,es eyes two, situated on each side thc head : feelers two, jointed; egg-shaped. The most familiar species are, 1. the A. siro, or common cheese-mite, which is a fa vonrite subject for microscopic observa tions. This insect is covered with hairs or bristles, which resemble in their struc ture the awns of barley, being, barbed on each side with numerous sharp-pointed processes. The mite is oviparous : from the eggs prveeed the young animals, re sembling the parents tn all respects, ex cept in the number of legs, which at first amount only to six, the pair from the head not making their appearance till after casting their first skin. The eggs in warm weather hatch in about a week, and the young animal may sometimes be seen for a day together struggling to get rid of its egg-shell. The mite is a very voracious animal, feasting equally upon animal and vegetable substances. It is also extremely tenacious of life ; for, upon the atithorit of Leewenhoek, though highly discredi table to his sense of humanity, we are as sured that a mite lived elevenweeks glued to a pin, in order for him to make observa tions on. 2. The A. exculcerans, or itch mite, is a species of considerable curiosity, on account of the structure of its limbs : it is slightly rounded, and of a flattened shape, with the thighs of the two upper pair of legs extremely thick and short : the two lower pair of legs have thick thighs, proceeding from a very slender base, and are extended into a long, stout, curved, and sharp-pointed bristle. Dr.
Bononio, an Italian physician, was the first who contended that the itch was oc ca.sioned by this insect, an account of which may be fount: in the Philosophical Transactions, No. 283. Dr. Baker is in clined to think that it constitutes the pao ra, a species ditch distinct from others confounded with it. 3. A. autumnalls, or harvest-bug, of a bright red colour, with the abdomen beset on its hind part with numerous white bristles. It attaches itself to the skin, and is with difficulty disen gaged. On the part whrre it fixes, it causes a ttnnour, about the size of a small bead, accompanied by R severe itching. The tido is of this species, st hich is to be found on dogs and other animals. Many of the acari attach themselves to insects of a larger kind, and hence they take their munes, as A. coleopterous, found on the black_ beetle. (See plate I. En; omology, fig. 1. and 2.) These insects, which are often very troublesome on plants, and in hot-houses, may be effectually destroyed by the fol lowing mixture. Take IAVO OLIIICCS of soft grecusoap, one ounce of coniinon turpen tine, and one ounce of flour of sulphur; pour upon these ingredients a gallon of bailing water, work the whole together with a whisk-, and let the mixture be used warm. This mixture may also be of use for preventing the mildew on the peach and apricot ; but it should never be used on fruit-trees near the time when their fruits are ripening. A strotag ley made of wood-ashes will likewise destroy the acti ri ; but plants are greatly' injured by this, and by briny and spirituous compositions.