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MITE
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MITE , a name applied to an See also:order of small See also:Arachnida, with which this See also:article deals, and to a See also:coin of very slight value. The origin of both would appear to be ultimately the same, viz. a See also:root mei-, implying something exceedingly small. It has been suggested that the name for the See also:animal comes from a secondary root of the root mei-, to cut, whence come such words as Goth. maitan, to cut, and Ger. messer, See also:knife. In this See also:case mite would mean " the biter " or " cutter." The coin was originally a Flemish See also:copper coin (Dutch mijt) See also:worth one-third or, according to some authorities, a smaller fraction of the Flemish penning, See also:penny. It has become a See also:common expression in See also:English for a coin of the smallest value, from its use to translate Gr. AenrrOv, two of which make a KOSpavTls, translated " See also:farthing " (See also:Mark xii. 43). In See also:zoology, " mite " is the common name for See also:minute members of the class Arachnida (q.v.), which, with the See also:ticks, constitute the order Acari. The word " mite," however, is merely a popular and convenient See also:term for certain See also:groups of Acari, and does not connote a natural assemblage as contrasted with the ticks (q.v.). Mites are either See also:free-living or parasitic throughout their lives or parasitic at certain periods and free-living at others. They are almost universally distributed, and are found wherever terrestrial vegetation, even of the lowliest See also:kind, occurs. They are spread from the See also:arctic to the See also:antarctic hemisphere, and inhabit alike the See also:land, fresh-See also:water streams and ponds, brackish marshes and the See also:sea. The largest See also:species, which occur in the tropics, reach barely See also:half an See also:inch in length; while the smallest, the most diminutive of the See also:Arthropoda, are invisible to the naked See also:eye. Mites are divided into a considerable number of families. The Bdellidae (Bdella) are free-living forms with See also:long antenniform palpi. The large tropical forms above mentioned belong to the genus Trombidium of the See also:family Trombidiidae. The members of this genus are covered with velvety See also:plush-like hairs, often of an exquisite See also:crimson See also:colour. The legs are adapted for crawling or See also:running, and the palpi are raptorial. They are non-parasitic in the adult See also:stage; but immature individuals of a See also:British species (T. holosericeum) are parasitic upon various animals (see See also:HARVEST See also:BuG). The Tetranychidae are nearly related to the last. A well-known example, Tetranychus telarius, spins webs on the backs of leaves, and is sometimes called the See also:money spider. The fresh-water mites or Hydrachnidae are generally beautifully coloured red or See also:green, and are commonly globular in shape. Their legs are furnished with long hairs for See also:swimming. The marine mites of the family Halacaridae, on the contrary, are not active swimmers but merely creep on the stems of seaweeds and zoophytes. The Gamasidae are mostly free-living forms with a thick exoskeleton, and are allied to the Ixodidae or ticks (q.v.). A common species is Gamasus coleoptratorum, the See also:females and See also:young of which may be found upon the common dung-See also:beetle. The Oribatidae or beetle-mites, so called from their resemblance to minute beetles, are non-parasitic, and often go through remark-able metamorphoses during development. The Sarcoptidae, as stated below, are mostly parasitic forms. Some members of this family, however, live in decaying animal substances, the best known perhaps being the See also:cheese-mite (Tyroglyphus siro) which infests cheese, especially Stilton, in thousands. An allied species (T. entomophagus) often causes See also:great damage to collections of See also:insects by destroying the dried specimens. They may be easily exterminated by application of benzine, which does not harm the contents of the See also:cabinet. From the economic standpoint the most important mites are those which are parasitic upon mammals and birds. They belong to the four families, Gamasidae, Trombidiidae, Sarcoptidae and Demodicidae. Most of the Gamasidae are free-living mites. The family, however, contains an aberrant genus, Dermanyssus, of which several species have been described, although they are all perhaps merely varieties of one and the same species commonly known as D. gallinae or D. avium. This species is found in See also:fowl-houses, dovecotes and See also:bird-cages. During the See also:day they lurk in cracks in the See also:floor, walls or perches, and emerge at See also:night to attack the roosting birds. They are a great pest, and frequently do much damage to birds both by sucking their See also:blood and by depriving them of See also:rest at night. They are sometimes transferred from birds to mammals. The Trombidiidae also are mostly free-living predaceous mites. A few, however, are parasitic upon mammals and birds, the best-known being Trombidium holosericeum, the larva of which attacks human beings, as well as chickens and other birds, sometimes producing considerable mortality amongst them (see HARVEST BUG). Another genus, Cheyletiella, affects rabbits as well as birds. Birds are also attacked by many species of Sarcoptidae, which according to the See also:organs infected are termed plumicolae (Analgesinae), epidermicolae (Epidermoptinae), and cysticolae (Cytoditinae). The Analgesinae (Pterolichus, Analges) live almost wholly upon and between the barbules of the feathers. They are found in nearly every species of bird without apparently affecting the See also:health in any way. The Epidermoptinae (Epidermoptes) occur on diseased fowls and live, as their name indicates, upon the skin at the See also:base of the feathers, where their presence gives rise to an See also:accumulation of yellowish scales. The Cytoditinae (Cytodites), on the other See also:hand, live in the subcutaneous or intermuscular connective See also:tissue See also:round the See also:respiratory organs, or in the See also:air sacs, especially of gallinaceous species. They also penetrate to certain See also:internal organs, and may become encysted and give rise to tubercle-like nodules. Sometimes they exist in such quantities in the air passages as to cause coughing and See also:asphyxia. The cutaneous mites, mentioned above, and others akin to them, produce no very marked disturbance in the skin of the species they infest. They merely suck the blood or feed upon the feathers, scurf and desquamating epidermis. Hence they are termed " non-psoric " mites. A certain number of species, however, called in contradistinction " psoric " mites, give rise by their bites, by the rapidity of their multiplication, and by the excavation of galleries in the skin, to a highly contagious disease known as See also:scabies or mange, which if not treated in See also:time produces the gravest results. These mites belong exclusively to the Sarcoptidae and Demodicidae. A variety of species are responsible for Sarcoptic mange, Sarcoptes mutans producing it in the feet of gallinaceous and passerine birds by burrowing beneath the scales and giving rise to a crusted exudation which pushes up beneath and between the scales. See also:Feather scabies or depluming scabies of poultry is caused by another species, S. laevis. Three genera of Sarcoptidae, namely Sarcoptes Chorioptes and Psoroptes cause mange or scabies in mammals,the mange produced by Sarcoptes being the most serious See also:form of the disease, because the females of the species which produces it, Sarcoptes scabiei, burrow beneath the skin and are more difficult to reach with acaricides. A considerable number of varieties of this species have been named after the hosts upon which they most commonly and typically occur, such as S. scabiei hominis, equi, bovis, caprae, ovis, cameli, lupi, vulpis, &c.; but they are not restricted to the mammals from which their names have been derived and structural See also:differences between them are often difficult to define and sometimes non-existant. Under favourable conditions the multiplication of this species is very rapid. It has been computed indeed that a single pair may give rise to one million and a half individuals in about three months. Psoroptes lives in the epidermic incrustations to which it gives rise, without, however, excavating subcutaneous burrows. One species, P. communis, is known to affect various domestic animals. Of the genus Chorioptes two species have been described on domestic animals, viz. Ch. symbiotes, which has the same mode of See also:life as Psoroptes communis and Ch. cynotis, which has been detected only in the ears of certain See also:carnivora such as See also:dogs, See also:cats and ferrets. Mange, if taken in time, can be cured by applications of See also:sulphur ointment or of sulphur mixed with an animal or See also:vegetable oil. Mites of the family Demodicidae give rise to a skin disease called " Demodecic or follicular mange," which is often serious and always difficult to cure on See also:account of the deep situation taken up by the parasites. These infest the See also:hair follicles and sebaceous glands, and are therefore termed Demodex folliculorum. These mites differ greatly from those previously noticed—in the reduction of their legs to See also:short three-jointed tubercles, and in the great See also:elongation of the See also:abdomen to form an annulated flexible postanal See also:area to the See also:body. They live not uncommonly in small See also:numbers in the skin of the human See also:face and their presence may never be detected. They also occur on dogs, pigs and other domesticated animals, as well as on mice and bats, and numerous varieties named after their hosts, hominis, bavis, canis, cati, &c., have been described, but they apparently differ from each other, principally in See also:size. The mites of the family Eriophyidae or Phytoptidae produce in various See also:plants pathological results analogous to those produced in animals by parasitical Sarcoptidae and by Demodicidae. As in the Demodicidae the abdomen is elongate and annulate, but the Eriophyidae differ from all other mites in having permanently lost the last two pairs of legs. The excrescences and patches they produce on leaves are called " See also:galls," the best known of which are perhaps the See also:nail-galls of the See also:lime caused by Eriophyes tiliae. A very large number of species have been described and named after the plants upon which they live. They often inflict very considerable loss upon See also:fruit-growers by destroying the growing buds of the trees. (R. I. Additional information and CommentsThere are no comments yet for this article.
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