NORTH AMEKICAN HYMENOPTERA. 



211 



9.— Pronotum shaiply margined anteriorly, the lateral tooth large and sharj) ; 

 longitudinal furrow of middle segment not broad, or widened medially 

 (markings usually whitish ; all the abdominal spots separated : scape 



and mandibles more or less whitish yellow) nioiltanus. 



Pronotum obtusely or not at all margined, the lateral tooth rather small and 

 blunt; longitudinal central furrow of middle segment broad and dis- 

 tinctly widened in the middle 10- 



10._Pronotum not margined ; posterior face of middle segment not ridged above ; 

 scape entirely black ; markings on fifth segment united, those on fourth 



nearly so • ■ • atriceps. 



Pronotum distinctly, though not strongly margined ; posterior face of middle 

 segment bounded above by a distinct ridge ; scape in part yellow ; mark- 

 ings on the abdomen all separated bruniieipes. 



11.— Scutelhnn with sparse punctures on anterior jiortion, striated posteriorly; 

 middle segment above generally with tolerably fine striations ; thorax 

 except the tubercles, rarely maculated ; femora entirely and inner por- 

 tion of tibia?, black parviilus. 



Scutellum finely striated throughout; middle segment above with coarse 

 folds or rugse ; pro- and metanotum always maculated ; femora at tips 



and greater part of tibia^., yellow corrugatus. 



12.— First joint of flagellum fully as long as the three following united ; posterior 



face of middle segment with feebly developed lateral ridges 13. 



First joint of flagellum scarcely as long as the three following united ; pos- 

 terior face of middle segment with scarcely a trace of lateral ridges (no 

 distinct transverse series of fovea} on middle segment). • .nigriiVoiis. 

 13.— Middle segment with a transverse series of strong fovea; separating the u])per 

 surface from the posterior face ; pedicellum more or less yellow. Siiecies 



Eastern. 



• obscuriis. 



Middle segment without a distinct series of foveas separating the upper sur- 

 face from posterior face; pedicellum black. Species Western. 



gracilissiinii!^. 



14__I^orsulum not striated, either finely or rugosely punctured 15. 



Dorsulum finely striated, transversely so on anterior poitiun, longitudinally 



on remainder '^~- 



15.— Pygidiura much narrowed apically, depressed or excavated 16. 



Pygidium broad, triangular, flat, not depressed or excavated 29. 



16.— Abdomen dorsally indistinctly punctured, or impunctate; pygidium always 

 with a lateral fringe of long, thick hairs ; head always finely and closely 



punctured . • ■ -"^ ' • 



Abdomen dorsally distinctly punctured, usually strongly so, particularly the 



first segment- 



19. 



17__Form broad, the first segment of abdomen not narrowed or lengthened, the 

 abdt)minal markings long, narrow ; pygidium with the apex obtuse or 

 rounded ; second ventral segment with large, much scattered punctures . 1 8. 

 Form narrower, the first segment of abdomen narrowed and lengthened, 

 though not very strongly so, the abdominal markings short, more or less 

 rounded; pygidium acutely pointed at apex; second ventral segment 

 with strong, separated, though not scattered, punctures. 



paiiciiuaciilatus. 



TR.\NS. AM. ENT. SOC. XXII. JUNE, 1895. 



