338 TWO SPECIES OF PARASITIC MITES. 



In colour the body, over the greater part of its surface, is of a 

 dirty white, though the epimera and the chitinous bands which en- 

 circle and support the legs are tinged with light yellowish-brown. In 

 shape the two sexes differ very much. Looking at the dorsal surface 

 the general outline of the male is ovate with the obtuse pole directed 

 forwards and rather strongly truncated, and from the middle of 

 this anterior end projects the conspicuous and almost quadrangular 

 rostrum, close to which on each side the anterior extremities take 

 their origin and point when at rest obliquely forwards and outwards. 

 The lateral margin of the body is marked by three constrictions 

 dividing it into four sub-equal segments, each of which bears a pair 

 of legs, hence the legs are arranged at almost equal distances from 

 each other along the sides of the body. This character creates a 

 marked distinction between this species and those of the genus 

 Sarcoptes, in which the legs, instead of being situated at equal 

 distances from each other, are arranged towards the anterior and 

 posterior ends of the body, a considerable distance separating the 

 insertions of the second and third pairs. On the other hand it 

 appears to point to a general relationship with the genus Myobia, 

 which further examination only serves to strengthen, though the 

 form of the female and the general course of development remove it 

 very far from this genus. The surface of the back is considerably 

 arched, rounding off along the sides into the belly which is flattened 

 towards the anterior end, but deeply hollowed out from the level of 

 the insertion of the second pair of legs backwards, evidently for the 

 purpose of receiving the female during copulation. In the female 

 the general shape is very different from that of the male. The body 

 is almost globular, being rounded on both the ventral and dorsal 

 surfaces ; the rostrum projects but very slightly beyond the anterior 

 end, and the legs are represented merely by little knobs situated 

 along the sides of the body. The male averages about .12 mm. in 

 length and .1 mm. in breadth. The female is not quite as large, 

 both length and breadth being about .1 mm. 



The body is covered with a thin, soft skin, which is smooth or 

 irregularly dotted over the greater part of the ventral and dorsal 

 surfaces, but along the sides in the male a few fine wrinkles can be 

 made out, following in their course the general outline of the body. 

 Imbedded in the skin are the epimera and the chitinous supports to 

 the legs, which will be described below. The skin is thus very like 



