242 AMERICAN HYMENOPTERA. 



4. Yellow pile of meso-pleura extending to bases of legs 5. 



Yellow pile of pleura not extending to bases of legs 7. 



5. All dorsal abdominal segments beyond the first two entirely covered 



with black pile ambiguus. 



Apical segments of abdomen bearing more or less yellow, light or 

 ferruginous pile 6. 



6. Dorsum of thorax having a clouded appearance, the pile being 



of yellow and black hairs thoroughly mixed sitkensis. 



Black band between the wings at least fairly well defined. 



frigidus. 



7. Malar space nearly or quite as long as it is wide at the apex 8. 



Malar space not nearly as long as it is wide at the apex ; apical 



segments without white pile 9. 



8. Some of the abdominal segments bearing considerable ferruginous- 



red pile; apical segments without white pile gelidlis. 



None of the abdominal segments bearing ferruginous pile ; apical 

 segments covered above with white pile alboanalis. 



9. Scutellum densely and entirely covered with yellow pile. 



henshawi. 

 At most with only a touch of yellow on the scutellum. 



occidentalis-nigroscutatus. 



10. Yellow pile of meso-pleura extending to bases of legs 11. 



Yellow pile of pleura not extending to bases of legs 21. 



11 . Thorax above entirely , or almost entirely , covered with yellow pile. . 12. 

 Thorax with a large amount of black pile between the bases of the 



wings 17. 



12. Malar space distinctly longer than it is wide at the apex 13. 



Malar space not distinctly longer than it is wide at the apex 14. 



13. Second dorsal abdominal segment usually entirely covered with 



yellow pile ; always more than half covered with yellow pile. 



vag-aiis. 



Second dorsal abdominal segment more than half covered with 



black pile bimaculatus. 



14. Some of the abdominal segments beyond the second bearing other 



than black pile rufociuctus. 



None of the abdominal segments beyond the second bearing other 

 than black pile 15. 



15. Ocelli large ; lateral ones much nearer to the margins of the eyes 



than to each other separatus. 



Ocelli small ; lateral ones not nearer to the margins of the eyes 

 than to each other 16. 



16. Second abdominal segment above entirely or in part covered with 



yellow pile vagans. 



Second abdominal segment above bearing little or no pile of a 

 color other than dark brown or black inipatiens. 



