DB. JOHNSTON ON THE ACARIDES OF BERWICKSHIRE. 293 



in the species examined hy him there are two small 

 brownish oval eyes situated towards the anterior rounded 

 angles, and very distant from each other.* In all other re- 

 spects the description of Dug^s applies strictly to our insect. 

 Some describe the legs as " longer than the body," which 

 may be the case in very small individuals ; and the same 

 authors tell us thai the mite lives on " spiders" as well as on 

 Phalangia,*f- an assertion which no observation of mine con- 

 firms. According to Dugbs the parasite infests the female 

 Phalangia more than the males, for the latter frequently re- 

 move them from the body by means of their palpi, which are 

 longer than in the females. To put themselves beyond the 

 reach of these organs, the mites fix themselves principally 

 behind the insertion of the posterior legs. 



Mons. A. Dug^s was, I believe, the first to discover the 

 real character of the mites of the genus Leptus. It had been 

 previously suspected that they were imperfect animals, but 

 our knowledge was merely conjectural until Dug^s ascertain- 

 ed that they were the larvae of Trombidia and of allied ge- 

 nera. In June of the year 1832 this naturalist collected se- 

 veral specimens of a Leptus from the Phalangium opilio and 

 cornutum, and placed them in closed vessels containing a little 

 earth. They buried themselves to a greater or less depth in 

 the interstices of the smaller lumps, where they became 

 motionless, and so remained for twenty days. Dug^s was 

 here able to see through the skin the development of the 

 eight legs, or at least the eight legs in a perfective state ; and 

 then he saw issue from this oviform smooth yellowish-red 

 nymph, a perfect Trombidium of a scarlet colour and small 

 size. This Trombidium he has described, and beautifully 

 figured, under the name of Tr. phalangii, and he admits that 

 it may be a variety of Tr. holosericeum. Until this point, 

 however, is decided, it would be premature to identify our 

 Leptus phalangii with the larva of the Trombidium phalangii 

 of Dug^s, for I am not aware that this is a native of Britain, 

 and certainly it has not yet been detected in the Eastern 



• S«pt. 6. — I tbought I detected these eyes as described by Dng^ to-day, but 

 uncertain whether the so-called eyes are not bristles, 

 f See Kirby and Spence, Introd. Eatom. iv. p. 672. 



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