ITCH MITE (Acarus scabiei or Sarcoptes scabiei), a minute icarus, supposed by some naturalists to be referred to by Aristotle in his 'Historia Anirnaliurn.' From the 12th century onward the connection of the mite and the itch was recognized but from 1800 to 1834 grave doubts were expressed. In that year, Renucci, a Corsican student, demonstrated the presence of the mite and investigation has since thrown much light on its structure and habits. The female is longer than the male, being visible to the naked eye, about one-fifth of an inch in length. In order to penetrate the horny layer of the epidermis, the mite assumes a nearly per pendicular, position; and to avoid as much trouble as possible, it usually selects such spots as give least resistance, such as the space be tween the fingers, the inside of the wrist, etc. Once fairly buried, it does not again come out, but burrows, and forms tortuous galleries within the skin. These galleries resemble the
mark which is formed when a pen is drawn lightly over the skin without causing a scratch. In young children, and in persons with a deli cate skin, they appear of grayish white color; while in persons with a coarse, dirty skin they are blackish. At certain intervals the galleries are pierced by small openings, for the admis sion of air. It is through these openings, which sometimes appear like very minute black dots, that the young escape. The vesicles character istic of the itch disease are attributed to a poison ejected by the mite. There are fewer males than females. (See licit). Consult Os born, (Insects Affecting Domestic Animals) (Washington 1896) and Raillet, (Zodlogie medi cale) (Paris 1895).