The Life-history of an Acarus, &c. By A. D. Michael. 385 



the cephalothorax are as follows : — Some short distance behind the 

 labium is a curved transverse band concave anteriorly ; from the 

 centre of this band the sternum runs straight backward in the 

 median line ; just passing an imaginary line drawn so as to join 

 the hind edges of the coxae of the second pair of legs ; then the 

 sternum bifurcates ; the branches are much narrower than the 

 true sternum, and they join the vulval ring (hereinafter spoken of) 

 at its antero-lateral part. The epimera from behind the first pair 

 of legs join the lateral branches of the sternum a little in front of 

 the centre; those from behind the second pair of legs, or the 

 apodemata prolonging them, join the vulval ring almost at the same 

 point as the same branches. The short epimera from behind the 

 third legs do not join any other sclerites. 



Legs of moderate length, the fourth pair about reaching the 

 posterior margin of the abdomen. The two front pairs thicker 

 than the two hind pairs. The first joints (coxae) rounded, the 

 proximal ends of the second joints small, thence the leg is gradually 

 increased in thickness until the distal ends of the bell-shaped third 

 joints, whence it gradually becomes thinner up to the distal end of 

 the tarsus. The tarsus is nearly as long as the three joints pre- 

 ceding it, varying a little in the difierent legs. There is a setiform 

 tactile hair on the fourth joint (tibia) of each leg, those on the two 

 front pairs being the largest. There are two strongly serrated 

 hairs on the second and one on the third joint of the first leg, and 

 one on the third joint of the second leg ; the serration of these 

 hairs is usually coarser at the distal than at the proximal ends 

 (fig. 12). There are also a few fine hairs on the tarsi, and one or 

 two on some of the other joints. The tarsi are terminated by a 

 long-shaped caruncle and fine single claw (as usual). 



Abdomen a long heart-shape, with the point anterior, and 

 the two rounded lobes forming the hind margin ; between them, 

 slightly on the dorsal surface, is the little tubular projection (bursa 

 copulatrix) characteristic of the females of the genus. The lobes 

 are considerably raised and rounded on the dorsal surface ; they 

 occupy the whole central part of nearly half the abdomen ; anterior 

 to them is a single broad lobe, less raised, occupying the central 

 part of the greater portion of the rest of the abdomen with two 

 irregular ridges upon it and a depressed trench outside it. Exterior 

 to this the abdomen (except its posterior part) has a broad raised 

 band, sloping upward towards its outer edge; this band has a 

 small raised lobe in the centre of its anterior part. There are four 

 minute points round the hind margin and a pair near the anterior 

 margin. The vulva of oviposition is very large ; placed far forward, 

 between the coxae of the third and fourth pairs of legs, and is sur- 

 rounded by a strong, chitinous, elliptical ring, the transverse axis 

 of which is the longer; this ring has a short, blunt, anterior, 



