THE GROUND BEETLES. 



121 



196 (750). Calattius impunctatus Say, Trans. Amer. Phil. Soc, 11. 1823, 

 45 ; ibid. II, 471. 



Elongate-oval. Black or piceous, shining ; antenna? and legs pale red- 

 dish-brown. Thorax slightly wider than long, sides broadly curved, hind 

 angles obtusely rounded, basal impressions not punctured. Elytral striae 

 deep, not punctured; intervals convex, the third with two distinct punc- 

 tures. Length 10.5-11.5 mm. 



Northern half of State ; scarce. June 17- August 21. 



XXXII. Platynus Bon. 1813. (Gr., "flat or depressed.") 



A large genus of black, green or bronzed beetles of medium size 

 and possessing the characters of the tribe. Palpi slender, with the 

 last two joints subequal; first, third and fourth joints of antenna? 

 of about the same length. Body usually somewhat slender with 

 the elytra nearly twice as wide as the head or thorax. Thorax very 

 variable in form, being either oval, cordate, square or rounded; 

 the margin sometimes barely visible. Elytra oval or oblong, some- 

 times elliptical, usually slightly sinuate at apex, sometimes almost 

 truncate ; the interval between the second and third striae with from 

 three to seven dorsal punctures. 



The members of the genus occur beneath cover in all kinds of 

 situations, some species being found only along the margins of 

 ponds, streams and lakes, others in high, dry upland w r oods. and 

 still others only in sandy locations. A number are known to hiber- 

 nate as imagoes. The two papers treating of the species of the 

 United States fauna are as follows : 



LeConte. — "Synopsis of the Species of Platynus and Allied 

 Genera Inhabiting the United States," in Proc. Phil. Acad. 

 Nat. SeL, VII, 1854, 35. 



LeConte. — " Synopsis of the North American Species of Platy- 

 nus," in Bull. Brook. Entom. Soc. II, 1879, 43-58. 



About 90 species of Platynus have been described from the 

 United States. Of these 41 are known to occur in Indiana. Since 

 the number of species is so large, the genus in the table which fol- 

 lows is first divided into groups, and these in turn into species. 



KEY TO GEOUPS OF INDIANA PLATYNUS. 



a. Elytra oval without humeral angles; side pieces of metathorax short, 

 not much longer than wide ; thorax ovate, narrowed behind, usually 

 strongly margined at sides. Group A. 



aa. Elytra with broadly rounded humeral angles; side pieces of metathorax 

 longer than wide. 

 6. Hind angles of thorax not rounded. 



c. Front tarsi without grooves, middle and hind tarsi with grooves 

 on the sides ; thorax narrowed behind. Group B. 



