530 GENERAL BIOLOGY 



Upper surface, if sculptured, not reticulate 26 



26. Metasternal groove broad and definite; length not 



over 15 mm. (10) Rhantus 



Metasternal groove narrow and indistinct (8) 



Colymbetes 



27. Prothorax with a narrow lateral raised margin (i) 



Eretes 

 Prothorax without such a margin 28 



28. Spurs of hind "tibiae acutely pointed at tip (4) 



Hydaticus 

 Spurs of hind tibiae emarginate at tip 29 



29. Elytra closely punctate (3) Acilius 



Elytra not punctate 30 



30. Middle femora beset with elongate setae (7) 



Thermonectes 



Middle femora beset with short and stout setae (3) 



Graphoderes 



Hydroporus undulatus. 



