THE PREDACEOUS DIVING BEETLES. 



221 



Lake, Laporte and Starke counties ; scarce. May 28-August 20. 



H. tenebrosus Lee, is known from New Jersey and Lake Su- 

 perior. 



Tribe II, COLYMBETINI. 



This tribe includes diving beetles of medium size or above, hav- 

 ing the tarsi distinctly 5-jointed, those of the males with the dilated 

 joints oblong. Nine genera are known to be represented in the 

 State, while a single species of another may occur. 



KEY TO INDIANA GENEEA OF COLYMBETINI. 



a. Semimembranous side pieces of first dorsal segment smooth ; smaller, 

 rarely 11 mm. 

 J). Hind tarsi with unequal claws. 



c. Spine of prosternum not sulcate; elytra with a pale pubescent spot 



on the inner face at apex. X. Ilybius. 



cc. Spine of prosternum deeply sulcate; elytra without pale spot. 



XI. Matus. 



hi). Hind tarsi with claws equal or nearly so. 



d. Last joint of palpi emarginate ; prosternal process much swollen 



along the middle. XII. Coptotomus. 



del. Last joint of palpi normal, not dilated or emarginate. 



e. Elytra deeply striate ; prosternal spine but little swollen at mid- 

 dle, XIII. COPELATUS. 



ee. Elytra not distinctly striate. 



/. Thorax not margined ; elytra beneath the lens showing numer- 

 ous very fine elongate stria? ; prosternum not sulcate. 



XIV. Agabetes. 



ff. Thorax margined at sides. 



g. Elytra with very fine longitudinal impressions ; hind legs 

 short and stout; wing of metasternum linear, strongly 

 curved. XV. Ilybiosoma. 



gg. Elytra without fine stria?; hind legs of medium length and 

 size ; wing of metasternum wedge-shaped. XVI. Agabus. 

 da. Semimembranous side pieces of first dorsal segment rugose; larger, 

 usually 12 or more mm. 

 7?. Upper surface conspicuously reticulate; thorax not margined on sides. 



SCUTOPTEEUS. 



Hh. Upper surface not reticulate. 



i. Elytra smooth, or in the female with short coarse lines ; metas- 



ternum with a broad, deep groove ; thorax margined. 



XVII. Rhantus. 



ii. Elytra with fine transverse wrinkles ; metasternum with a narrow 



indistinct groove ; thorax not margined. XVTII. Colymretes. 



The rugosities referred to under aa in the above table are near 

 the first spiracle, and I he elytron must be raised to see them prop- 

 erly. 



