COLEOPTERA. GYRlNIDiE. 105 



in both sexes ; but Erichson conceives there must be some error 

 in this. The Rev. F. W. Hope possesses a most remarkable hermaph- 

 rodite specimen of this genus, one side having male, and the other 

 partial female characters. 



There has been considerable confusion introduced into the 

 nomenclature of the species of this genus, Linnaeus having led the 

 way by reversing the sexes of D. marginalis. The British species 

 may be easily distinguished by the form of the two points which 

 terminate the posterior coxae (ordinarily misnamed the sternum, 

 fig. 5. 7.). Notwithstanding their large size, these insects are 

 subject to the attacks of a minute parasite, described by M. 

 Audouin (Bull. Soc Phllom., 1822, and Zool. Jotirn.), under the 

 name of Achlysia Dytisci, but which the recent investigations of M. 

 Duges have proved to be the immature state of one of the Water- 

 mites (Hydrachnae), and which affixes itself to the thin membrane with 

 which the upper surface of the abdomen is covered. (See also Bur- 

 meister in Isis, 1831). 



The large exotic species belong almost exclusively to the genus 

 Cybister Curtis, of which a single species only is European (C. 

 Roselii, an extremely rare British insect). The remainder are dis- 

 tributed over very wide tracts of country ; thus one species is found 

 in Guinea, the Cape of Good Hope, Madagascar, the Mauritius, and 

 the Indian Archipelago ; and in like manner, according to Dejean, 

 Eunectes sticticus is found in India, the American Islands and France. 

 The other exotic genera do not merit any particular notice. 



The family GYRiNiDiK*, corresponding with the Linna^an genus 

 Gyrinus, consists of a small but remarkable group of beetles, which. 



* BiBLIOGR. TO THE GyRINID^. 



Forssberff. Nova Acta. Acad. IJpsal. vol. viii. (Descriptions of 24 species). 



Modeer, in Vetenskeps, Acad. Handl. 1770. 



Klvg, in Symbol. Physic, and Coleopt. Madagascar. 



Dufour. Anna). Sc. Nat., Oct. 1824. (Internal Anatomy.) 



Sturm. Deiitchsland's Faima, vol. x. 



Laporte. Etudes Entomologiques, p. 2. 



Audouin and Brullt. Hist. Nat. vol. v. 



Erichson. Kafer du Mark. Brandb. 



