538 Peculiar Species of Mite 



Art. XII. O71 a peculiar Species of Mite parasitical on Slugs, 

 By the Rev. Leonard Jenyns, F.L.S. 



During a recent examination of our British Z/imaces, I 

 observed a peculiar parasite infesting some of the larger spe- 

 cies of that family, which, at jfirst, I was inclined to think 

 might prove new. I have since ascertained that it was known 

 to Reaumur, and described by him in the Memoires de VAca- 

 demie Roy ale des Sciences, so long ago as in the year 1710. I 

 have also met with a short notice respecting it in Shaw's 

 Naturalisfs Miscellany. As, however, Reaumur's account of 

 this insect differs from mine in one or two particulars, while 

 that of Shaw's is a mere allusion to it, appended to his 

 description of one of our British slugs, I have thought that 

 some farther publication of its history, accompanied by a 

 correct figure, might not be without interest; especially to 

 those persons who, being unacquainted with the memoir above- 

 mentioned, may possibly have no knowledge whatever of the 

 existence of this insect. 



The parasite in question belongs to the ^caridae of La- 

 marck ; a tribe, perhaps, better known by the English name 

 of mites ; and, although extremely minute, is interesting, on 

 account both of its usual place of residence and the singu- 

 larity of its habits. I first noticed it on some specimens of 

 the J^lmax variegatus of Ferussac, which were obtained from 

 a cellar in Cambridge, and thought that, like many of its con- 

 geners, it was a species of a wandering disposition, which had 

 only strayed upon these animals accidentally. I afterwards, 

 however, found it upon the same kind of slug, obtained from 

 another source, and have since met with it in great plenty at 

 S waff ham Bulbeck upon the common black slug (Arion em- 

 piricorum Fer,)> I now feel satisfied that these insects are 

 strictly parasites attached to this family of molluscous animals ; 

 an idea which receives full confirmation from the observations 

 of the two authors above alluded to. 



One of the most striking features in the history of this 

 little insect is the circumstance of its not confining its abode 

 to the external surface of the slug, but often retiring within 

 the body of that animal ; effecting its entrance by means of 

 the lateral foramen which leads to the cavity of the lungs. 

 Indeed, I am inclined to think that this cavity is its prin- 

 cipal residence, whence it only comes forth occasionally, to 

 ramble upon the surface of the body. In one instance, I con- 

 fined in a close box a slug which, to all appearance, was free 

 from parasites. On opening the box a day or two afterwards, 

 I observed very many crawling about the slug externally, all 



