On Aquatic Carnivorous Colcoptera or DytiscidcB. 



389 



II. 9. — Group Htdroporini. 



Front and middle tarsi 4-jointed (with a small additional joint occasionally 

 visible at the base of the terminal joint) ; mesosternum but little visible, being 

 placed at such an angle with the metasternum that it is much concealed between 

 this and the prothorax : hind coxal cavities nearly or quite contiguous; ventral 

 segments not soldered to coxe&; prosternal process acuminate behind. 



There are ten genera comprised in the Hydroporini. I find it difficult to make 

 a dichotomous key that woukl be practically useful for their identification, and 

 have therefore drawn up the following series of abbreviated characters ; these can 

 be glanced through in a few minutes and the genus in this manner ascertained with 

 certainty. 



Elytral ligula free and abrupt, terminal joint of front tarsus very sliort in 1 

 comparison witli tlio third joLut. Three species from the eastern \ 

 portion of the INIediterrauean region. J 



HYPUOPORUS. 

 (Vide^. 390.) 



Elytral ligida free, ahrupt, terminal joint of front tarsus not very sliort in ] 



comparison with the third joint, although often much concealed by | CCELAMBUS. 



the deep fissure of the latter. Numerous species in the European and j {Vide \). 394.) 



North American regions. J 



Elytral ligida abrupt on the posterior fiice, gradually raised in front ; hind ] 

 coxal cavities approximate ; posterior portion of epipleuras very 

 .narrow ; humeral area of epipleura limited behind by a well-marked 

 raised line. Six sjiecies, extending from Madagascar to Southern 

 Europe. J 



Elytral i-idge very little developed ; posterior coxal cavities much exposed 

 and a good deal sej^arated ; posterior portioir of epipleura veiy narrow ; 

 hind tibia with only the serial punctures on the infero-extemal face. 

 Three species peculiar to Australia. 



Elytral ligula absent ; posterior portion of epijileura comparatively Ijruad ; ") 

 hind tibia with only the serial ^junctures on the infero-external ftice ; | 

 posterior femora slender, with rounded outer angle. Four species f 

 found in Australia and Tasmania. J 



Posterior portion of epipleura comparatively 

 on the infero external aspect ; the trii 

 scarcely visible. Eight species found in Australia and New Zealand. J 



jroad ; hind tiljia [iimctured "I 

 the true foui-th joint of front tarsus j- 



True fourth joint of front tarsus quite conspicuous, distinctly disengaged ^ 

 from the lobes of the third joint : (this structure more exaggerated in ! 

 the males than in the females). Eight species found in Australia and , 

 Tasmania. J 



Hmd tibia only with serial punctures on the infero-external aspect. 

 Terminal poi-tion of epipleura rather broad : posterior femora stout ; 

 their postero-external angle sharply defined. Six species found in 

 Australia and Tasmania. 



IIEROPHYDRUS. 

 {Vide IX 392.) 



PAROSTER. 

 {Vide^. 391.) 



CIIOSTONECTES. 

 {Vide\x 408.) 



ANTIPORUS. 

 {Vide IK 410.) 



NECTEROSOMA. 



(Fj'rfep. 412.) 



MACROPORUS. 

 {Videp. 416.) 



3 E 2 



