Acaropsis mericourti, Moq. Tand.
[This mite has been described from three specimens found in pus which flowed from an abscess in the ear of a naval officer, produced by inflammation of the auditory passage. Where the mites came from we do not know, as they were found near the Bank of Newfoundland. This genus of Acari has enormous mandibles and a peculiar tracheal system; two ungues and appendages to the tarsi.—F. V. T.]
Family. Sarcoptidæ (Itch Mites).
Small mites without eyes and tracheæ, and with delicate, transversely striated cuticle. The mouth parts form a cone, over which the shield-shaped upper lip protrudes; the cheliceræ are chelate; the pedipalpi (or maxillary palpi) have three joints; the legs are short and compact, and composed of five segments; the terminal joints have pedunculated suckers (ambulacra) or a long bristle. The larvæ are six-legged. They live on or under the skin of birds and mammals, on which they produce the skin disease known as scabies, or itch.
[The Sarcoptidæ attack the hairs, feathers or epidermis of birds, animals and man, living as permanent parasites. The punctures they produce are followed by the formation of more or less thick crusts or scabs, beneath which the mites live and breed (so called scab, mange and itch). Most are oviparous, some ovoviviparous. The eggs are minute, ovoid, with a thin semi-transparent shell. They incubate in a few days, varying from two to ten or eleven, as a rule. Generally sarcoptic diseases lie dormant in winter and revive in spring and summer in man; but in animals with long wool, such as sheep, they are most active during winter, although revival of active reproduction takes place in spring.
[Speaking generally, for the Sarcoptidæ there are three distinct stages in the development of the male, four in the female, as follows:—
[(1) The larva. In this stage only three pairs of legs occur.
[(2) The nymph, in which a fourth pair of legs appear, and which thus approaches the adult; but so far no sexual organs occur. Nymphs are of two sizes—the smaller being future males, the larger females.
[(3) The next stage in the female is the age of puberty, the female now being provided with a vulvo-anal slit; this so-called pubescent female is fertilized by the male. The male then dies. But the female again casts her skin and enters another stage—
[(4) The ovigerous female—the egg-laying female—which has differently modified legs.