Dr. Johnston on the Acarides of Berwickshire. 159 



bifid, sparingly hispid. Mandibles shaped like the rostrum, 

 and of the same length, armed with two minute but unequal 

 claws. Palpi of the same coluur, but considerably slenderer 

 than the legs, filiform, inserted near the base of the rostrum, 

 and longer than it by the ultimate joint, five-jointed ; basal joint 

 minute ; the second elongated, with a very few scattered short 

 setse ; third and fourth very small and equal, with setae on the 

 top of each ; terminal joint about a third snorter than the second, 

 contracted at its origin, sparingly hispid, the somewhat truncate 

 apex armed with two sharp setse of nearly its own length. Legs 

 eight, equidistant, of the colour of the body and about its 

 length, tapering normally, somewhat hispid, the setse either 

 patent or pointing downwards : first pair shortest, second and 

 third nearly equal, the hinder pair longer, all about equal in 

 thickness ; basal joint small, the second or femoral about four 

 times as long, the third about half the length of this, the fourth 

 or knee still shorter, the fifth distinctly slenderer and as long as 

 the femoral ; the sixth elongated, tapered, armed with more nu- 

 merous and stronger setae, and terminated with a pedunculated 

 small hairy vesicle and a pair of slender sharp claws trimmed 

 with hairs on the inner aspect. 



This mite is a small species, and of the usual Apion-like shape, 

 possessing only a moderate degree of quickness in its walk. It 

 recovers its position with difficulty when laid on its back on a 

 level surface ; but, as it lives amongst moss, this accident can 

 rarely or never occur to it. 



The specific character may be derived from the colour, which 

 is a pale yellow tinted with red on the body and all its members ; 

 but the large dusky spot which occupies the back is what ren- 

 ders the little creature most obvious to the eye. I believe it to 

 be the Bdella dorsata of Gervais. The name suits our animal 

 well ; but there are some points in the description which seem 

 to mark a difference, especially the apparent absence of eyes, 

 of which, in B. dorsata, there are four, of a waxen red colour, 

 imbedded in the black part of the back. Now, in our mite there 

 is a red spot anterior to this dorsal patch, and near the middle 

 of the back, but I could not determine that it was made up of 

 eyes, nor would analogy lead us so to conclude, for the eyes, in 

 this genus, are lateral when present. 



Our species belongs to the genus Bdella as defined by A. 

 Duges, Ann. des Sc. Nat. 2de Ser. ii. p. 44. 



36 ACARUS DESTRUCTOR. 



Acarus destructor, Tuch. Gmel. iii. 707. 

 Mite minute, of a uniform white colour. Body divided into 

 three segments, ovate-oblong, narrow in front, rounded behind, 



