(5 A REVTSIOlSr OF THE TYROftLYPHTD^. 



STRUCTURAL CHARACTERISTICS. 



The TyroglyphicUe are pale-colored, soft-bodied mites, devoid of 

 trachea?; with small, appressed palpi; usuall}' with prominent chelate 

 mandibles; with moderately long legs* ending in one claw, and often 

 a sucker or caroncle; and with a l)ody about twice as long as broad, 

 and })roadest behind the middle. There is commonly a distinct suture 

 between cephalothorax and abdomen. There are no eyes, unless cer- 

 tain spots on the front margin of certain H^^popi and on (Urjjoglyphus 

 represent these organs. The dorsum bears a few, usuall}' long, hairs, 

 in size and arrangement constant for each species. The legs have 

 bristles, tine hairs, and sometimes distinct spines, the more prominent 

 of which are constant in position for each species. One long bristle 

 near tip of the penultimate joint is especially prominent; another is 

 a thickened or clavate hair near base of tarsi I and II, and is probal)l3' 

 a sense organ. The latter is always upon this joint, altho several 

 authors have figured it on the penultimate joint in some species. On 

 the venter are two apertures; the genital is usuallj" elongate and 

 situate between hind coxfe, and there are often U-shaped marks each 

 side of it known as the genital suckers, which can be protruded. The 

 anal opening is toward the tip of the body, and is often but an elongate 

 slit, with a sucking disk each side of it. In the genus Glyciphagus 

 these openings are much larger, and the genital sometimes occupies 

 the entire area between the coxa^. 



There are but slight differences in structure between the sexes; but 

 in some cases the male has one pair of legs enlarged, or there may be 

 two forms of the male. In some species the male has two little suckers 

 on the hind tarsi; in others there is a curved plumose bristle on the 

 basal part of front legs. The males are smaller than the females, and 

 have a less tumid abdomen. 



TRANSFORMATIONS. 



The transformations of the Tyroglyphidie are among the most mar- 

 velous of the animal kingdom. All tyroglj'phids la}^ eggs, often of 

 large size, which are scattered haphazard over the infested material. 

 The young on hatching have six legs and at molting obtain two more. 

 Thenceforward their life history may take the simple and direct path 

 to the adult condition, but often passes through a stage called the 

 Ilypopus. This Hypojytis is a very different creature than that from 

 which it developed — the octopod nymph. Its body is hard and chiti- 

 nous, there is no mouth orifice, and no distinct mouth parts; the legs 

 are short and ill adapted to walking. On its ventral surface near the 

 tip is an area separated from the general surface and provided with 



