450 U. S. NATIONAL MUSEUM BULLETIN 216 



7. Propodeum and pronotum completely rugulosopunctate so that none of the 



surface is smooth; thorax about 2.6 as long as high . 7. alaskensis (Rohwer) 



Propodeum and pronotum not completely rugulosopunctate, half or more of 



their surface relatively smooth (though punctate) ; thorax about 2.4 as 



long as high 8 



8. Temples strongly flaring, the head about 1.09 as wide across widest place on 



temples as across eyes; hind femur partly to entirely black or blackish, at 

 least its apical 0.2 infuscate; middle coxa fulvous . 23. vicinum (Cresson) 

 Temples not flaring or less strongly flaring, the head not more than 1.05 as 

 wide across temples as across eyes ; hind femur fulvous to black, if black or 

 blackish the middle coxa also black or blackish 9 



9. Hind coxa partly or entirely brown to black. (Some males of parvum and 



a few of dichrous are variable in this character and will run through either 



half of the couplet.) 10 



Hind coxa entirely fulvous 16 



10. Second tergitc with sharp fine punctures and with fine wrinkling between the 



punctures; trough of pronotum with ridges crossing at about a 40° angle; 

 middle and hind femora black; propodeal spines practically absent. 



8. aethiops (Cresson) 



Second tergite with weak, very fine punctures, often smooth between the 



punctures ; trough of pronotum with ridges crossing at about an 85° angle . 1 1 



11. Hind femur black 12 



Hind femur fulvous to medium brown 13 



12. Trough of pronotum with about 8 cross ridges . . . 18. atripes (Rohwer) 

 Trough of pronotum without cross ridges, or with a few weak ones next to the 



epomia 19. dreisbachi, new species 



13. Hind coxa and femur concolorous, both varying from fulvous brown to 



blackish brown 15. parvum, new species, in part 



Hind coxa (at least in part) much darker than hind femur, the coxa varying 

 from entirely black to fulvous with more or less of its basal part fuscous; 

 hind femur fulvous to medium brown 14 



14. Hind first trochanter blackish or dark brown, or when fulvous the second 



tergite entirely ferruginous 9. abdominale (Cresson) 



Hind first trochanter fulvous; abdomen entirely black or rarely with restricted 

 ferruginous areas 15 



15. Propodeal teeth usually about 0.3 as long as their basal width. (Not always 



separable from males of O. dichrous.) . . . 16. brevicaudus (Cushman) 

 Propodeal teeth usually about 0.8 as long as their basal width. 



17. dichrous (Rohwer), a few specimens 



16. Front face of hind femur with the punctures much sparser at its lower 0.3 ± 



than at its upper 0.3 ±, the punctures on its lower part not more than half 

 as dense as on the upper part; trough of pronotum without transverse 

 ridges ; range ; eastern half of North America, except for curium .... 17 

 Front face of hind femur with the punctures nearly as dense at its lower 0.3 ± 

 as on its upper 0.3 ±, the punctures on its lower part usually more than 

 half as dense as on its upper part; range: western half of North America, 

 except for canadense 21 



17. Second and third tergites ferruginous; flagellum with about 30 segments; 



range: California 13. curtum, new species 



Second and third tergites black (as is the rest of abdomen) ; flagellum with 

 35 to 45 segments; range: eastern half of North America 18 



