88 NORTH AMERICAN 



Head large, much wider than the elytra at base.. ..41. scahaosais. 

 Head small, narrower than the elytra at base. 



Body very robust ; elytra very feebly impressed on the suture at 

 the base ; longitudinal elevation of head rounded. 



42. vespertiiius. 

 Body much more slender ; elytra strongly impressed on the suture 

 at the base ; longitudinal elevation of head rather acute. 



43. convictor. 

 Species less than 3.0 mm. in length. 



Longitudinal elevation of head acute and prominent; canaliculation of 



pronotum short, deep, and conspicuous 44. confllSUS. 



Longitudinal elevation rather obscure, broadly rounded ; canaliculation 

 of pronotum very obscure, being simply a very feeble erosion, in 

 some cases almost obsolete. 

 Prothorax widest distinctly before the middle. 



Larger species. Legs black 45. iiioniatus. 



Smaller species. Legs fuscous 4U. placidllS. 



Prothorax widest at or behind the middle. 

 Sides of prothorax nearly straight in front of the broadest section, 

 at which point they are rather acutely angnlate. Massachusetts. 



47. mendax. 



Sides of prothorax strongly rounded anteriorly, not angulate, broadly 



rounded at the widest section 48. erieusis. 



Subgroup b. 



Head large, much wider than the. elytra at base 49. spliwrops. 



Head equal in width to the elytra at base 50. ill iB it a lis. 



Head distinctly narrower than the elytra at base. 



Head extremely small ; interocular surface broad; eyes narrow. Massa- 

 chusetts 51. pi ailo. 



Head slightly broader ; interocular surface narrow ; eyes wide and very 

 convex. Arizona 52. iiicilltus. 



Subgroup c. 



Elytral suture much shorter than the pronotum 53. pteroliracliys. 



Elytral suture distinctly longer than the pronotum. 



Prothorax distinctly elongated ; legs black throughout ; form robust ; elytra 

 finely, deeply, evenly, and very closely punctate ; surface rough and 



nearly opaque i 54. corvus. 



Prothorax about as wide as long; legs not black; form more slender; 

 elytra coarsely punctate : surface generally shining. 



Large species, 4.2-4.5 mm. in length 55. maritillllis. 



Small species, not exceeding 3.0 mm. in length. 



Form slender ; punctures of elytra almost entirely isolated. White 



Mountains, N. II 56. llioiltaillis. 



Form more robust; somewhat depressed; punctures of elytra gene- 

 rally close and coalescent. Colorado and British Columbia. 



57. alpicola. 



