258 AMERICAN HYMENOPTERA. 



33. Outer surface of hind tibiae concaved borealis. 



Outer surface of hind tibiae convex 34. 



34. Femora vs^ith considerable light pile pennsylvaniciis. 



Femora with little or no light pile sonorus. 



35. Greater part of face very densely covered with yellow pile with no 



admixture of black hairs vosneseiiskii. 



Face not bearing a great amount of yellow pile, if any, what there 

 is being mixed with black hairs 36. 



36. Malar space half as long as the eye arcticus. 



Malar space not nearly half the length of the eye 37. 



37. Third dorsal abdominal segment covered entirely, or for the most 



part, with black pile 38. 



Third dorsal segment covered with yellow pile terricola. 



38. Apical abdominal segments with white pile. 



terrestris var. moderatiis. 

 Apical abdominal segments with no white pile californicus. 



39. Apex of abdomen usually bearing a considerable amount of dull 



ferruginous-red pile ; some of the tibias usually more or less 

 distinctly fringed with ferruginous hairs ; pile of scutellum 

 often, but not always, with a very strong admixture of black 

 hairs pennsylvanicus. 



Apex of abdomen always black ; all of the tibiae black, except the 

 posterior ones on the inside ; pile of scutellum never with a 

 strong admixture of black hairs fervidus. 



Third dorsal abdominal segment black ; scutellum mostly yellow. 



affinis. 



40. Third or fourth dorsal abdominal segment entirely covered with 



black pile 41. 



Neither the third nor the fourth dorsal abdominal segment thus 

 covered 43. 



41. Abdomen without yellow pile above except on the first segment. 



impatiens. 



Abdomen with more or less yellow pile on other segments than 



the first above 42. 



42. Second dorsal abdominal segment bearing considerable black pile, 



especially on the sides, and usually on the apical half also 



(all black in case of californicus) 54. 



Abdomen having little or no black pile on the second dorsal seg- 

 ment 56. 



43. Hind metatarsi with long hairs 44. 



Hind metatarsi without long hairs appositiis. 



44. Some of the dorsal abdominal segments covered with ferruginous- 



red pile 45 . 



None of the dorsal abdominal segments so covered perplexus. 



45. Second dorsal abdominal segment covered with yellow pile. 



flavifrons and centralis. 



