DR. JOHNSTOK 0» TffE ACARIDES OF BERWICKSHIRE. 309 



the two anterior pairs rather distant from the posterior, the 

 first pair slenderer and longer than the others and nearly as 

 long as the body, the others about equal ; 6-jointed, the three 

 basilar joints short, the 4th twice as long as the second with 

 a single bristle, the 5th elongate cylindrical with three or 

 four bristles near the lower end, the 6th still longer than the 

 fifth, tapered, with two bristles on its upper half, one on each 

 side, with a very short stout one on the inner side ; all the 

 bristles point downwards, and the lowermost project far be- 

 yond the extremity of the joint, which is armed with two 

 unequal curved claws. 



The rostrum contains an awl-shaped stylette (Fig. 2), which 

 can be pushed out beyond the snout. The furniture of the 

 mouth is one of the most beautiful structures that can be 

 seen anywhere, nor is it possible to view it, as it is brought 

 out in detail under the microscope, without an expression of 

 wonder. The coriaceous part of the skin, when highly mag- 

 nified, appears striolated in a very delicate manner. 



This mite has much of the aspect of a Gamasus, but 

 differs essentially in the structure of the mouth. We are 

 told that it is found in books kept in damp places, particu- 

 larly about the backs, and is very injurious by eating away 

 the paste with which the sheets have been glued together. 

 My specimens were taken by Mr. Hardy in two of his insect 

 boxes. On two different occasions, Mr. Hardy found it drag- 

 ging away the larvce of Atropus pulsatorius, and he thinks it 

 probable that it feeds on them rather than on paste. " Hav- 

 ing placed," he writes me, " a box on the ground in a damp 

 place, I found it peopled by large numbers of the Atropos, of 

 very great size, and at the same time by Gamasus coleoptra- 

 torum, which, I believe, had the same errand as the Acarus 

 eruditus." 



The young have 8 legs. Schranck saw it come from the egg 

 itself with that number. — Kirby and Spence, Introd. Entom. 

 iii. p. 107. 



17. ACAKUS QENICULATUS. Lifl. 



Acarus niger, geniculis femorum globosis, Lia, Faun. Suec 

 350. — Ac. petrarum niger, abdomine globoso lucido, femori- 

 bus subclavatis, Geoff. Hist Insect, ii. 626. — Acarus genicula- 

 tus, lin, Syst 1025. Turt. Gmel. iii. 705. Lin. Faun. Suec. 



J 



