. Text book of zoology. Zoology. 284 Arthropoda. abundant in small pieces of water, where it builds a beU-Uke web, tbe cavity of which, is filled with air, carried by the animal from the surface of the water in its velvety covering of hairs. Order 3. Acarina (Mites). The Mites are small, frequently even microscopic Arachnids, in which the cephalothorax and abdomen are generally fused into a single mass. They possess from one to three pairs of eyes, or none at all. The mouth-parts are usually short. The pedipalpi, as well as the cheliceras, may be chelate, they are sometimes used for biting, so
. Text book of zoology. Zoology. 284 Arthropoda. abundant in small pieces of water, where it builds a beU-Uke web, tbe cavity of which, is filled with air, carried by the animal from the surface of the water in its velvety covering of hairs. Order 3. Acarina (Mites). The Mites are small, frequently even microscopic Arachnids, in which the cephalothorax and abdomen are generally fused into a single mass. They possess from one to three pairs of eyes, or none at all. The mouth-parts are usually short. The pedipalpi, as well as the cheliceras, may be chelate, they are sometimes used for biting, sometimes for stabbing. A heart has only been demon- strated in some of the Acarines; special respiratory organs are frequently absent, but in many there is a tracheal system, opening by a pair of stigmata. On hatching, the Mites possess only three pairs of legs, the fourth pair develops later; in other respects also, the larvae may differ more or less from the adult. Many undergo a resting period before moulting. The genital aperture, as in other Araohnida, is situated anteriorly on the ventral sur- face of the abdomen. In some females {Tyroglyphus, probably also iu the Sarcoptidse), there is, besides, the ordinary genital opening, a second one pos- teriorly, just in front of the anus, by which the spermatozoa are received during copulation, whilst the anterior serves as the oviducal pore. 1. rrom6ii£w(i», red, velvety, quadi'angular animals, some of The larvae live as parasites on The Water-. Fig. 231. Diagram of the anatomy of a Tyro- glyphus ; legs cut off. a anus, c cerebral ganglion, d mesenteron, ij oheKoera, 1:2 pedipalp, Jlf Malpighian tube, n ventral ganglionic mass, Ov ovary; $ aper- ture of the oviduct, $ ' copulatory aperture.—Orig. which are among the largest of the Mites. Phalangium, Spiders and Insects; the adults ai'e predaceous. mites (Hydrachna and others), are roimdish animals, often of a red colour, which swim about in the water by means of their haiiy le
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1896
