THE MITES 101 



Family III. Sarcoptid^ 



Mange, scab, or itch mites. Acarina (p. 94). — The body has the 

 cephalothorax and abdomen- fused; it is white or reddish in color. The 

 cuticular surface is transversely striated and provided with bristles, 

 sometimes with short dorsal spines. The mouth parts are beak-hke, 

 extending forward, and covered by the protruding labrum; chelicerse 

 scissors-Uke; maxillary palpi small and three-segmented. The legs are 

 short and stout, have five segments, and are disposed in two groups of 

 two pairs each, the anterior pairs, usually the larger and near the mouth 

 parts, the posterior pairs near the abdomen. The tarsi commonly ter- 

 minate in one or two hooklets; they may terminate in a long bristle or 

 an ambulatory sucker, often upon a stalk which may be segmented. 

 Respiratory organs are absent; respiration cutaneous. There are no 

 eyes. All are scarcely visible without the aid of magnification. 



There are frequently well-marked sexual differences. Males are con- 

 siderably smaller than the females. In some males the fourth pair of 

 legs is very small, and there may be plate-like copulatory suckers at 

 the base of the abdomen with abdominal prolongations. As to the 

 presence or absence of bristles or stalked suckers, the tarsi may ter- 

 minate differently in the two sexes. 



Development. — ^As already stated in the general reference to the 

 Acarina, the Sarcoptidse have three distinct stages in the development of 

 the male, four in the female. After sexual maturity and fertilization of 

 the female, the male usually dies. Following fertihzation the female 

 molts and enters upon her fourth or ovigerous stage, — the egg-bearing 

 stage, recognizable by the presence of the genital pore upon the anterior 

 ventral surface of the abdomen, through which the eggs are extruded. 



The rapidity with which these acari breed is very great. It has been 

 estimated that one female sarcopt will produce in a subepidermic gallery 

 about fifteen individuals, from which, after ninety days, there may be 

 1,500,000 descendants constituting the sixth generation. 



The family includes a number of genera differing in their mode of 

 attack and location upon the host. All are permanently parasitic. Of 

 these, six, namely: Sarcoptes, Psoroptes, Chorioptes, Notoedres, Cnem- 

 idocoptes, and Otodectes are considered here. The characteristics and 

 habits of the principal genera met with follow. 



Sarcoptes (Fig. 64). Sarcoptidse (p. 101). — The body is rounded or 

 shghtly oval; the mouth parts short and about as broad as long. Upon 

 the dorsal surface of the body are a number of cone-like prominences 

 and twenty spines, the latter short, thick, and grouped as follows: four- 

 teen upon the abdomen, seven to the right and seven to the left side; 

 six upon the cephalothorax, three to the right and three to the left. 

 The legs are thick and conical, the posterior pair being nearly or quite 



