260 



FAMILY VT. IIYDROPHILIMG. 



sometimes indistinct. The beetles usually occur in numbers along 

 the edges of ponds, lakes and streams and rise to the surface when 

 the water is made turbid. Five species have been taken in Indiana, 

 while another may occur. 



KEY TO INDIANA SPECIES OF PI IILII YDKTS. 



. Above paler, brownish-yellow to pale pit-eons. 



b. Prosteruum distinctly carinate; length 3.5-4.5 nun. 



503. NEBULOSUS. 

 bb. Prosternuui uot carinate. 



c. Smaller, not over 4 mm. ; mesosternal lamina very feeble, the front 



edge without distinct angle. 504. OCHRACEUS. 



cc. Larger, 46 mm. ; mesosternal lamina prominent, with a distinct 



angular projection. 



d. Thorax with a large discal piceous space. 505. HAMILTONI. 



dd. Thorax entirely dull yellow. IHKFUSUS. 



an. Above black or pic-eons black, the margins sometimes pale. 



e. Larger, 6.5-7 mm.; transversely very convex. 506. CINCTIS. 



ec. Smaller, not over 5.5 mm. ; subdepressed. 507. PERPLEXUS. 



503 (1(326). PHILHYDRUS NEBULOSUS Say, Long's Exped., II, 1824, 277; 



ibid. I, 183. 



Oval, slightly oblong, convex. Above variable from pale to dull brown- 

 ish-yellow, shining; head and uuder-surface piceous. Thorax and elytra 

 sparsely and indistinctly punctured, the usual rows of coarser punctures 

 scarcely visible. Length 3.5-4.5 mm. 



Throughout the State; common. May 15-Octobcr 21. 



504 (1630). PHILHYDRUS OCHRACEUS Melsh.. Proc. Phil. Acad. Nat. Sci., 



II, 1S44, 101. 



Elliptical, less convex. Above pale piceous or dull 

 smoky brown, shining; head darker, with a pale space 

 in front of each eye ; margins of thorax and elytra paler : 

 beneath piceous, the tibia 1 and tarsi paler. Thorax and 

 f\ elytra distinctly and rather closely punctate, the dorsal 

 rows very indistinct. Length 3.5-4 mm. (Fig. 128.) 



Northern half of State ; common ; less so in the 

 southern portion. April 23-October 26. Resem- 

 bles nebulosiis, but smaller: prosternum not cari- 

 nate and punctures of upper surface more distinct. 



PHILHYDRUS HAMILTONI Horn, Trans. Amer. Ent. Soc., XVII, 



3890, 249. 



Oblong-oval, moderately convex. Above piceous-yellow or dull brown- 

 ish-yellow ; head piceous; disk of thorax with an indefinite semicircular 

 space darker. Punctures of thorax not very close; those of elytra a little 

 coarser, the discal rows faint. Length 4.5-5.5 mm. 



Lake, Starke and Laporte counties; frequent. April 23-Sep- 



Fig. 128. X 'Jo. 

 (Original.) 



505 (9315). 



