THE WATER SCATEN6EE BEETLES. 



255 



400 (1585). Hydrophilus ovatus Zieg., Proe. Phil. Acad. Nat. Sci., II, 

 1844, 45. 

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

 piceous ; antennae 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, 

 traeted by electric light. 



491 (1586). HyDBOPHILLTS TKIANGTJLARIS 



Say, Journ. Phil. Acad. 



Nat. Sci., Ill, 1823, 201 ; 



ibid. II, 128. 

 More elongate, less convex. Above of 

 same hue as ovatus; 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. Prostemal 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. 



May 25-October 8. Often at- 



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

 /, antenna; g, front tarsus of female; A, same of ^ 

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

 (After Riley.) 



VI. Teopisteenus Sol. 1834. (Gr., "keel -f breast") 



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

 in ponds, lakes and slow-flowing 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 OE TEOPISTERNUS. 



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

 stripes. 

 6. Thorax and elytra narrowly margined with yellow. 



492. NIMIJATl s. 



6B. 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. 



49?.. MIXTUS. 



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

 equal in size or nearly so. 

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

 tinct. 494. SIBL^VIS, 



[17— 23402^ : I 



