SOME PAEASITIC ACARl. 



403 



ward, while the abdomen is somewhat raised ; thus the creature 

 has the appearance o£ possessing caput, thorax, aud abdomen. 

 The abdomen has two very long hairs at its hinder end, and there 

 are two smaller, but still large, hairs on the lateral edge between 

 the second and third legs ; and two on the cephalothorax, as in the 

 other species, besides two sparse longitudinal rows of smaller 

 hairs on both divisions of the body. The first and second legs 

 are like those of the male, but the claws are shorter. The third 

 and fourth legs resemble the third pair of the male, but the claws 

 again are shorter, but, on the other hand, they are broader. 

 These great holding-claws in this species are much wider in pro- 

 portion than those of M. musculinus ; indeed, their breadth is 

 very remarkable. On the ventral surface the epimera of the first 

 pair of legs join in the median line and are prolonged by a short 

 sternum (so-called) ; those of the second pair of legs are forked 

 at their distal ends. Posterior to these, and almost touching those 

 of the third pair, are two conspicuous chitinous pieces of rather 

 more than half-a-circle shape with their outer corners slightly 

 prolonged ; the chitinous pieces protect the vulva, which lies 

 between the third and fourth pairs of legs. 



The Nymph. — The nymph is very similar in form to the male, 

 but without the square posterior projections ; there is only one 

 pair of large hairs posteriorly. The fourth pair of legs are similar 

 to the third, as in the female. The constriction between cephalo- 

 thorax and abdomen is very marked. Neither pair of legs are 

 nearly so long as the third pair of the male. 



The Larva. — Almost diamond- shaped ; of course there are not 

 any fourth legs, but the tliird pair are placed near the posterior 

 end of the body, giving a very singular appearance. Otherwise 

 the larva resembles the nymph. Both differ considerably from 

 those of M. musculinus. 



Habitat. Parasitic upon the field-vole (Arvicola agrestis). 



Stmbiotes tripilis, n. sp. (PI. XXVI. fig. 8.) Female. 



mm. 



Length about "SB 



Breadth about '26 



Length of legs : 1st and 2nd pairs about '15 



8rd pair about '06 



4th pair about '03 



Length of longest hair on 3rd tarsus about '70 



,, ,, on hind margin of body about '40 



