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 
