THE ACARIXA OR MITES. 



71 



joint enlarged. The mandibles are chelate, slender, and exsertile. Thorell made a 

 new family for the genus, but other writers consider it related closely to Parasitidae. 

 The food habits and transformations are unknown. 



Family PARASITIDiE. 



The parasitid (figs. 135, 136) mites are among those 

 best known to collectors of insects, since many species 

 are very common, and others spend part of their life 

 attached to beetles and other insects. Typically these 

 mites have a hard coriaceous integument, but there 

 are many exceptions to this rule. They are quite fiat, 

 broad, and with rather short legs. They have no 

 eyes, but the sense of touch is very highly developed 

 through many hairs on the legs and body. Some 

 species are slow in movements and are apt to feign 

 death when disturbed, but others can run with consid- 

 erable rapidity. The mouth parts, in many species, 

 may be completely withdrawn into the body of the 

 mite. The mandibles are normally chelate and the 

 fingers toothed. Sometimes they are greatly elongate 

 and styliform, and thus fitted for piercing; in a few 

 cases the movable finger is lacking. In many species 

 there is a projection or appendage arising near the base 

 of the fingers known sometimes as the "spur, " some- 

 times as the "flagellum." Beneath the mandibles is 

 a large piece, the hypostome. It is bifid and each side 

 ends in an elongate corneous point. Between the two 

 corneous points is a long fleshy part, the lingula. 

 Above the mouth there is in many forms a thin plate, often toothed, known as the 

 epistome. The palpi are prominent and usually five-jointed. In the Uropodinse 

 the palpi are scarcely \dsible, as the body projects so much in front. The legs 



are of moderate length, usually 

 , ., p slender, and arise close together, 



in a row each side. In the Uio- 

 podinee the anterior pair is sepa- 

 rated from the others and their 

 coxae are nearly contiguous. The 

 body is commonly pro\dded with 

 coriaceous plates or shields, the 

 position and shape of which 

 are characteristic of each species. 

 These plates sometimes nearly 

 cover the entire body. Their 

 position and names may be ob- 

 served from the accompanying illustrations (figs. 135, 136). The scutum, sur- 

 rounding the coxal cavities, is known as the parapodia; in some cases it forms a 

 little projection behind the hind coxa, which is then called a "squama parapodia." 

 There are some small shields or pieces which are often of importance; a pair just behind 

 the fourth coxse are called the "metapodia;" a pair just behind coxae I are knoA^-n 

 as the "jugularia," and a pair behind sternal plate the "metasternalia." Frequently 

 there are differences between the sexes in the arrangement of the plates, and in the 

 males of many species the ventral plates are mostly coalesced. The female genital 

 opening is commonly under the anterior margin of a plate (the genital) which ends 



Fig. 135.— Venter of Parasitus: a, Pe- 

 ritreme; b, jugularia; c, sternal 

 plate; d, metapodia; c, genital 

 plate; /, anal plate. (Author's il- 

 lustration.) 



Fig. 136. — Side view of a Parasitus: e, Epistome; 

 p, peritreme; v, anal plate. (Author's illustration.) 



