The young (though there is, probably, a still earlier hexapodous stage) of this Sarcoptid has an elongated, oblong, flattened body, with four short legs, provided with a few bristle-like hairs, and ending in a stalked sucker, by aid of which the mite is enabled to walk over smooth, hard surfaces. The body is square at the end, with a slight median indentation, and four long bristles of equal length. They remained motionless in the groove on the barb of the feather, and when removed seemed very inert and sluggish. A succeeding stage of this mite, which may be called the pupal, is considerably smaller than the larva and looks somewhat like the adult, the body having become shorter and broader. The adult is a most singular form, its body being rudely ovate, with the head sunken between the fore legs, which are considerably smaller than the second pair, while the third pair are twice as large as the second pair, and directed backwards, and the fourth pair are very small, not reaching the extremity of the body, which is deeply cleft and supports four long bristles on each side of the cleft, while other bristles are attached to the legs and body, giving the creature, originally ill-shapen, a haggard, unkempt appearance. The two stigmata or breathing pores open near the cleft in the end of the body, and the external opening of the oviduct is situated between the largest and third pair of legs. No males were observed. In a species of Acarus (Tyroglyphus), somewhat like the Cheese mite, which we have alive at the time of writing, in a box containing the remains of a Lucanus larva, which they seem to have consumed, as both young and old are swarming there by myriads, the young are oval and like the adults, except that they are six-legged, the fourth pair growing out after a succeeding moult. Such is a brief summary of what has been generally known regarding the metamorphoses of a few species of mites. In a few kinds no males have been found; the females have been isolated after being hatched, and yet have been known to lay eggs, which produced young without the interposition of the males. This parthenogenesis has been noticed in several species. [Illustration: 144. Cheyletus.] These insects often suddenly appear in vast numbers on various articles of food and about houses, so as to be very annoying. Mr. J. J. H. Gregory, of Marblehead, Mass., has found a mite allied to the European species here figured (Fig. 144) very injurious to the seeds of the cabbage, which it sucked dry. This is an interesting form, and we have called it Cheyletus seminivorus It is of medium size, and especially noticeable from the tripartite palpi, which are divided into an outer, long, curved, claw-like lobe, with two rounded teeth at the base, and two inner, slender lobes pectinated on the inner side, the third innermost lobe being minute. The beak terminates in a sharp blade-like point.