THE PREDAOEOUS DIVING BEETLES. 221 



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



H. tenetrosus 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-.iointed, those of the males with the dilated 

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

 State, while a single species of another may occur. 



KEY TO INDIANA GBNEKA OP C0LYM"=1ETIN1. 



«. Semimembraiious side pieces of first dorsal segment smooth ; smaller, 

 rarely 11 mm. 

 6. Hind tarsi with unequal claws. 



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

 on the inner face at apex. X. Iltbius. 



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



XI. Matus. 

 1>T). Hind tarsi with claws equal or nearly so. 



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

 along the middle. XII. Coptotomus. 



(Jd. Last joint of palpi normal, not dilated or emarginate. 



0. 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 strife; prosternum not sulcate. 



XIV. Aqabetes. 



ff. Thorax margined at sides. . , 



g. Elytra with very iine longitudinal impressions ; hind legs 



Short and stout ; wing of metastemum linear, strongly 



curved. XV. Iiybiosoma. 



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



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



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



usually 12 or more mm. 



ft. Upper surface conspicuously reticulate ; thorax not margined on sides. 



SCUTOPTBBIJS. 



hli. Upper surface not reticulate. 



i. Elytra smooth, or in the female with short cdars'e lines; metas- 

 ternum with a broad, deep groove ; thorax margined. 



XVII. RlIANTUS. 



H. Elytra with fine transverse wrinkles; metasternum with a narr(]\\- 

 indistinct groove; thorax not margined. XVIIT. Colymketes. 



The r'liu-dsitics refci'icd tt> under (i<i in llic alxivc tabluarc iioir 

 1h(' first spii-iielc, and the elytron must l)e raised to sec them pro|)- 

 erly. 



