CLASS V. IKSECTA. 



159 



Sp. 1. Hyd. Byhneri. Black; front and margin of the thorax femigine- 



ous, margins of the ehtra yellow with black spots. 

 Dytiscus parapleurus. Harsh. 

 Inhabits ponds : is of rare occurrence near London. 



Genus 62. ACILIUS. Leach's Zool. Misc. vol. iii. 

 External maxillari/ palpi with the second joint obconic, third elongate 



obconic, fourth longer, nearly cylindrical, and roimded at its apex. 



Anterior tarsi of tlie male patellilbrm : elj/tra of the female sulcated. 

 Sp. 1. Ac. sulcatus. 

 Dytiscus sulcatus of authors. 

 Inhabits ponds and stagnant waters, and is very conmion. 



Genus 63. DYTICUS. Geof., Illig., Leach. Dytisccs. Linn£, 



Fair., Latr., Marsh. 



External maxillary palpi with the third and following joint of equal 

 length ; the last gradually increasing from the middle : anterior tarsi 

 of the male patelliform : {PL 3. Jig. 13. a.) eli/tra of the female sul- 

 cated. 



Sp. 1 . Di/t. marginalis. Ovate, olive-black above, luteous red beneath ; 

 the scutellum of the same colour with the eljtra : clypeus, whole 

 margin of the thorax, and border of the el,\-tra, red clay-colour; bi- 

 furcature of the sternum lanceolate. (PI. 3. fg. 13. c.) 



Inhabits Europe. In Britain it is common in ponds at aU seasons of 

 the year. 



Dytiscus circumiiexus of Fabricius is abundant in the ponds near 

 London. It is distinsuished from marginalis by its more elongate 

 shape, by the bifurcate process of the sternum being spine-shaped, 

 and by the colour of the scutellum, which is invariably ferruginous. 

 (P/. 3. Jig. 13. b. sternum.) 



Fam. IV. Gtrixid-I. Leach. 



Internal maxillary palpi composed of one part : antenna very short : 

 eyes dinded so as to appear as four ; four hinder Jeet compressed, fo- 

 liaceous, formed for swimming. 



Genus 64. GYRINUS. Linn., Fabr , Latr., Gyll, Leach, 

 " * Elytra nailed, zcixh punctured struz.'^ Leach. 

 Sp. 1. Gyr. Xatator. Oval: el jtra with punctured stris ; the inflescd 

 margin testaceous. {PI. 2. Jig. 2. a. antenna tnagnijied. b, the hinder 

 leg magnified.) 

 Inhabits stagnant waters. 



« ** Elytra smooth, villose." Leach. 

 Sp. 2. Gyr. zUlosus. Fabr., GyU. 

 G%Tinus Moderii. Marsham. 

 Inhabits rivers and running waters. 



