THE WATER SCAVENGER BEETLES. 



255 



May 25-October 8. Often at- 



490 (1585). Hydrophilus ovAtus Zieg., Proe. Phil. Acad. Nat. Sci., II, 



1844, 45. 



Less elongate, more convex. Above black with an olive tinge ; beneath 

 piceous ; antenna? and tarsi paler. Abdomen pubescent, the last three seg- 

 ments narrowly smooth at middle, without yellow spots at sides. Pro- 

 sternal prominence, in which front end of sternal spine fits, open in front. 

 Length 31-33 mm. 



Southern half of State ; frequent, 

 tracted by electric light. 



491 (15S6). Hydrophilus triangularis 



Say, Journ. Phil. Acad. 



Nat. Sci., Ill, 1823, 201 ; 



ibid. II, 128. 

 More elongate, less convex. Above of 

 same hue as ouatus; beneath darker, 

 more shining, the abdominal segments 

 with more or less distinct triangular 

 yellow spots at sides. First segment pu- 

 bescent, the remainder broadly smooth 

 at middle. Prosternal prominence closed 

 in front. Length 34-37 mm. ( Fig. 126. ) 



Throughout the .State; common. 

 March 19- October 27. Sometimes 

 attracted by thousands to electric 

 lights in Indianapolis and the 

 larger cities. Hibernates as imago. 



Fig. 126. b, H. triangularis Say, natural size; 

 /, antenna; g, front tarsus of female; h, same of 

 male, all magnified; i, side view of sternal spine. 

 (After Riley.) 



VI. Tropisternus Sol. 1834. (Gr., "keel + breast.") 



Smooth, shining, oval insects, mostly black above ; very common 

 in ponds, lakes and slow-tiowing streams. Nine species, including 

 Nos. 1588 to 1595 of the Henshaw "Catalogue," belong to this 

 genus, five of which have been taken in Indiana. 



KEY TO INDIANA SPECIES OF TEOPISTEENUS. 



a. Prosternal prominence or groove closed in front ; elytra without yellow 

 stripes. 



&. Thorax and elytra narrowly margined with yellow. 



492. NIMBATUS. 



h~b. Thorax and elytra entirely black above. 



c. Front part of sternal crest very finely and indistinctly punctured ; 

 elytra with very fine and coarser punctures intermixed. 



493. mixtus. 



cc. Front part of sternal crest distinctly punctured; elytral punctures 

 equal in size or nearly so. 

 (I. Form elongate-oval; elytral punctures very minute and indis 

 tinct. 494. scbljats 



[17—23402] 



