MITES, small parasitic members of the Arachnidan order Acarina, which also contains the ticks (q.v.), mange-insects and similar forms. The body is compact, not divided into separate regions, as head, thorax and abdomen; and they appear, as they are, greatly inferior to the spiders. They have eight legs, eyes useless, or nearly so, two spiracles only, and mouths with sharp, beak-like mandibles, fitted for biting or for piercing the skin of the animal on which they reside or prey by imbibing its juices. The mites undergo a metamorphosis, the larva passing through a series of changes varying with the species. The species are many, and are parasitic on a large variety of animals, and on mankind. In America, for instance, no less than 18 kinds infest poultry, of which the red mite (Dermanyssus gallince) and the chicken itch-mite (Sarcoptes nutans), attacking the feet, are the most commonly met with. A contagious disease among chickens is caused by a scrt of mange-mite (Cytodites nudus) that flourishes in the air-passages, setting up inflammation of the lungs. The most serious disease of sheep is caused by the scab-mite (Psoroptes com munis), varieties of which also produce °scab° in horses, cattle, goats and rabbits.
Household pests are the cheese-mites of two species that now have a world-wide distribu tion; but they will flourish equally well in other sorts of stored goods. A cheese once attacked will speedily be reduced to a powdery mass of mites, cast-off skins and excrements, the result of the amazingly rapid multiplication of the mites, and the fact that they produce living young. The new generation matures quickly and at once continues the production. When the stock of food is wholly consumed the youngest and oldest mites die, but those in vigorous middle age assume a scale-like quiescent form, called the hypopus stage, which is able to subsist indefinitely without activity or food. Finally a cockroach, mouse or some other
small creature comes near enough to be seized by the hypopus, when it clings to a hair, crawls to the surface of the skin, begins to feed and sets up a new colony.
Of the mites inhabiting the human body the itch-mites (Sarcoptes scabes) is the most import ant and fortunately is disappearing. It affects a large number of hairy kinds of animals in all parts of the world, as well as man, and lives continuously on its host. The itching sensation denoting its presence is caused by the female mites burrowing beneath the skin, where the eggs are laid, and by the young feeding on the tissues before making their way to the surface in search of breeding-mates. Mange (q.v.) in dogs is the result of the presence of a simi lar mite (S. conic). Workers in copra are annoyed by related mites; and soft sugar is sometimes infested with mites of the genus Tyroglyphus, which cause °grocer's itch° in those who handle it. A common mite whose presence gives little if any trouble is the one (Demodex) found in the ublackheads,° or blackish follicles that disfigure the noses of some of us.
That desperately annoying pest of autumn in some places, the minute red °harvest-bugs° of the genus Leptus, inhabit vegetation whence they attach themselves to man and other ani mals and begin to burrow in the skin causing an intolerable heat and itching, often resulting in bad sores. Consult authorities in Economic Entomology and Hygiene: especially Ealand, 'Insects and Man' (New York 1915). See Tim