82 AMERICAN HYMENOPTERA. 



26. The first four dorsal abdominal segments clothed entirely with 



yellow pile 27. 



Not all the first four dorsal segments clothed entirely with yellow 

 pile 30. 



27. Either the mesopleura clothed with yellow pile to the bases of the 



legs, or the femora with considerable light pile, or both. .28. 



The mesopleura mostly dark and the femora with little or no light 



pile sonoi-us. 



28. Apex of abdomen usually with a more or less noticeable amount of 



ferruginous pile ; the mesopleura with their lower portion 

 usually more or less noticeably darkened ; pile of scutellum 

 often with more or less strong admixture of dark hairs. 



pennsylvauicus. 



Apex of abdomen never with ferruginous pile ; mesopleura always 



clothed entirely with yellow pile to the bases of the legs ; 



scutellum never with an admixture of black hairs 29 



29. Yellow pile pale straw-yellow in color ; the sixth dorsal abdominal 



segment clothed with mostly black pile ferviflus. 



Yellow pile of a richer, more golden, yellow color ; the sixth 

 dorsal abdominal segment clothed with mostly yellow pile. 



souonise. 



30. Dorsum of thorax unicolorous 31. 



Dorsum of thorax bicolored 38. 



31 . Mesopleura yellow 32. 



Mesopleura entirely or mostly dark 34. 



32. The two apical dorsal abdominal segments bearing pale ferrugin- 



ous pile nioiiteziiiiiae. 



The two apical dorsal segments entirely dark 33. 



33. The sides of the second and third dorsal abdominal segments with 



more or less reddish-ferruginous pile pulclier. 



The second and third dorsal segments with no reddish-ferruginous 

 pile ephippiatus. 



34. Dorsum of thorax yellow, reddish-ferruginous, or fusco-rufous..35. 

 Dorsum of thorax black 36. 



35. The last three or four dorsal abdominal segments yellow or rufo- 



ferruginous emilin^. 



Only the third and fourth dorsal abdominal segments bearing pile 

 of a color other than black steiiidaclmeri. 



36. The apical dorsal abdominal segment bearing considerable ferru- 



ginous pile 37. 



The apical dorsal segment with little or no ferruginous pile. 



iiiexicauus. 



37. The fifth and sixth dorsal abdominal segments black incdiiis. 



The fifth and sixth dorsal segments yellow or yellowish. 



doliclioceplialiis. 



