250 AMERICAN HYMENOPTERA. 



7. Fringes of corbiculse with a distinctly ferruginous tinge ; black 



interalar band extending back on to the scutellum in a sharp V. 



edwardsii. 



Fringes of corbiculae without a ferruginous tinge ; black interalar 



band usually not very distinctly marked ; never extending 



in a sharp V onto the scutellum rufocinctus. 



8. Clypeus completely impunctate, smooth and shining, except cor- 



ners 10. 



Clypeus somewhat sparsely punctured over its entire surface 9. 



9. First abdominal segment above covered chiefly with black pile. 



occidentalis. 



First abdominal segment above covered chiefly with light or yellow 



pile edwardsii. 



10. The last two abdominal segments black above Ijorealis. 



Only the last segment black above appositus. 



11. Third and fourth dorsal abdominal segments entirely covered with 



black pile 12. 



Third and fourth dorsal abdominal segments not both entirely 

 covered with black pile 18. 



12. Fifth dorsal abdominal segment covered with yellow pile 13. 



Fifth dorsal abdominal segment black above 14. 



13. Scutellum densely covered with bright yellow pile ; fringes of cor- 



biculae usually black cockerelli. 



Scutellum generally darkly shaded ; fringes of corbiculae usually 

 strongly tinged with ferruginous sitkeiisis. 



14. Pile covering scutellum conspicuously darker than that covering 



the anterior part of the thorax above anibiguus. 



Pile covering scutellum not conspicuously darker than that cover- 

 ing the anterior part of the thorax above 15. 



15. Yellow pile on scutellum and on anterior part of thorax above with 



black hairs strongly intermixed flavifroiis. 



Yellow pile on scutellum and on anterior part of thorax above 

 without admixture of black hairs 16. 



16. Malar space longer than its width at the apex pleiiralis. 



Malar space not longer than its width at the apex 17. 



17. A touch of yellow pile present on the lateral margins of the third 



abdominal segment mornionoruni. 



No touch of yellow pile on lateral margins of third segment. 



separatiis. 



18. First four segments of the abdomen above all covered with yellow 



or tawny pile 19. 



Not all the first four abdominal segments above covered with 

 tawny or yellow pile 20. 



19. Last two abdominal segments black ; clypeus more or less punctate. 



centralis. 



