On Aquatic Carnivorous Coleoptera or Dytiscidw. 881 



Group 9. 



Hind coxse moderate or rather large, wings of metasternum moderate ; pro- 

 sternal process acuminate compressed, finely margined ; swimming legs moderately 

 stout ; male claws of front feet rather long ; elytra marked with yellow. 



This is by no means a natural group ; of Agabus lineolus and A. desertorum I have 

 no specimens at present, and jalace them here only from my imperfect notes, their 

 males moreover are quite unknown to me. These two species have the prosternal 

 process very compressed, the metasternal grove very rudimentary and narrow ; 

 their hind coxte are little developed. 



In Colymbetes tseniolatus and A. disintegratus, the yellow colour and marks 

 are much developed, the metasternal cavity is narrow and indefinite, and the swim- 

 ming legs are only moderately stout. 



In Dytiscus didymus the yellow marks are merely some dots on the wing-cases, 

 the metasternal groove is better developed, and the swimming legs are stout. 



Group 10. 



Anterior tarsi of male never greatly incrassate, their claws more or less elongate, 

 their undersurface bearing distinct but never large palettes. Prosternal process 

 elongate, never broad, but little compressed, and not carinate ; metasternal groove 

 rather long ; wings of metasternum rather large, hind coxae moderately developed, 

 their front border much arched : swimming legs moderately slender. 



The group is not a natural one. Agabus strigulosus Lee, has the prosternal 

 process rather short and punctulate, and the male front tarsi are clothed beneath 

 with glandular hairs amongst which are three rows of small palettes : and it, (as 

 well as A. austini) has the uppersurface very distinctly reticulate, the reticulation 

 forming large meshes. In the other species the prosternal process is shining and 

 impunctate. 



In Dytiscus nebulosus, D. conspersus, and A. austini, the claws of the posterior 

 feet are longer than in the other species, and they have the prosternal process 

 broader. 



D. nebulosus and D. conspersus, have the clothing of the male tarsi forming 

 longer hairs and less distinct palettes than in the other species. 



A. subfuscatus is a species which in appearance and structure stands about equally 

 as near to Dytiscus paludosus and A. japonicus of group 2 as it does to D. congener 

 of this group. 



Agabus austini and Dytiscus striolatus make a slight approach to group 20, 

 and the clothing of the male tarsi can scarcely be said to show any palettes. 



Group 11. 



Outline of thorax and elytra discontinuous, male front tarsi slender but Avith 

 long claws ; prosternal process rather small, nearly flat, very finely margined, feebly 



