'2i'A) FAlMII;^ \l.- in liK'Ol'll I I.I D.K. 



sometimes indistinct. The beetles usually oecui- in munbers along 

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

 the water is made tur1)id. Five species have been tak(Mi in Indiana, 

 while another may occur-. 



KEY TO INDIANA Sl'ECIKS OK I'l 1 1 1. 1 1 V DUl S. 



«. Above jialer, brownish-yellow to imlc piccdiis. 



/(. I'l-dstcriium (listiiictly carinate; Iciiutli :;..''i 4.") nun. 



50;!. NEuui^osrs. 

 hb. Prosteruuni not carinate. 



c. Smaller, not over -I nun.; nicsosternal lamina very feeble, the front 



edge without distinct angle. 5U4. ocukackls. 



cc. Larger, 4-G mm. ; mesosternal lamina prominent, with a distinct 



angular pro.1ection. 



d. Thorax with a large discal piceous space. 5U5. ii.A.MiLTONi. 



del. Thorax entirely dull yellow. difflsis. 



aa. Above black or piceous black, the margins sometimes pale. 



c. Larger. (;.5-7 mm. ; transversely very convex. 500. cinctls. 



ee. Smaller, not over 5.5 mm. ; subdepressed. 507. perplexus. 



503 (lOL'C)). PiiiLHYDKis NEBULOSUs Say, Long's Exped., II, 1824, 277; 



ibid. 1. 183. 

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

 ish-yellow, shining; head and uuder-surt'ace piceous. Thorax and elytra 

 sparsely and indistinctly i)unctured. the usual rows of coarser punctures 

 scarcely visible. Length 3.5 4.5 mm. 



Throughout the State; common. May 15-October 24. 



504 (3030). PiiiLHYDRUS ocHRACEt's Molsh., Proc. I'hil. Acad. Nat. Sci., 



II, 1844, 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 thora.x atid elytra paler ; 

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

 elytra distinctly and rather closely punctate, the dorsal 

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



Northern half of State ; conunon ; less so in the 

 southern i)ortion. April 2o-0etober 26. Resem- 

 bles iichulosus, but smaller; ])rosternum not cari- 

 nate and punctures of upper surface more distinct. 



505 (9315). Philhy'drus hamiltoni Horn. Trans. Amer. Ent. Soc, XVII, 



1890, 249. 

 Oblong-oval, moderatelj^ convex. AbnYC piceous-yellow or dull brown- 

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

 space darker. Punctures of thorax imt very close ; those of elytra a little 

 coarser, the discal rows faint. Length 4.."')-5.5 nun. 



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



