ANSWER THIS FIRST! The Western portion of the guide is usable with caution, let us know if you have problems resolving any species | Abdomen, T1, hair color, not counting the hairs present on the anterior portion of the segment that faces the propodeum | Abdomen, T2, hair color | Abdomen, T3, hair color | Abdomen, T4, hair color | Abdomen, T5, hair color | Females, parasitic vs non-parasitic queens and workers | Head, color of hairs just behind ocelli | Head, long hairs located just above antennae - Note that there is usually a fuzz of shorter, highly branched hairs that are often yellow, at the base of the longer hairs, these short hairs should be ignored | Head, malar space, the space between mid-point of attachment of mandible and very bottom of eye compared to width of base of mandible | Head, ocelli, position relative to imaginary line across tops of eyes | Male, parasitic vs non-parasitic | Queen vs Worker - General guidance - It is often difficult to tell queens from workers without a direct comparison between the two | Sex, antennal segment number | State or province where bee was collected | Subgenus | The opening page offers a limited set of characters from which to choose. Click on any trait states that you can confidently assess, and then use the SEARCH button to activate your choices. This will return a set of species matches on the left . Next, select SIMPLIFY and the screen will present a new set of characters. | Thorax, below base of front wing, hair color | Thorax, scutellum, color of hairs | Thorax, scutum, color of hairs on REAR HALF of plate

Check boxes for all that apply. If uncertain, skip character or select several states. Then click on any search button.
Navigate with above index or scroll bar.
Number scored for a state is in green.
1. The opening page offers a limited set of characters from which to choose. Click on any trait states that you can confidently assess, and then use the SEARCH button to activate your choices. This will return a set of species matches on the left . Next, select SIMPLIFY and the screen will present a new set of characters.    [Explain]

2. ANSWER THIS FIRST! The Western portion of the guide is usable with caution, let us know if you have problems resolving any species

221. EASTERN - Click here for completed and well tested guide to eastern species    672. Click here for guide for all species including western species   
3. State or province where bee was collected    [Explain]

26AK    6AL    6AR    41AZ    46Alberta    29Arctic tundra or taiga    52British Columbia    67CA    46CO    11CT    6DC    6DE    3FL    8GA    20IA    49ID    11IL    11IN    9KS    8KY    3LA    11MA    8MD    11ME    11MI    22MN    6MO    6MS    49MT    21Manitoba    8NC    25ND    28NE    11NH    8NJ    38NM    47NV    11NY    8New Brunswick    12Newfoundland and Labrador    14Northwest Territories    8Nova Scotia    8OH    61OR    21Ontario    11PA    8Prince Edward Island    23Quebec    8RI    8SC    34SD    31Saskatchewan    8TN    6TX    49UT    8VA    11VT    58WA    19WI    9WV    46WY    21Yukon   
4. Sex, antennal segment number

44Female, 12    23Male, 13   


5. Queen vs Worker - General guidance - It is often difficult to tell queens from workers without a direct comparison between the two

21Queen, usually much larger, active and most abundant earlier in spring    20Worker, smaller and often more variable in size, active from mid-spring into summer   
6. Females, parasitic vs non-parasitic queens and workers

42Non-Parasitic, common species, outer part of tibia largely hairless, flat, or concave, and rimmed by long hairs    2Parasitic, rare to uncommon species, hairs on outer face of tibia uniform in density and length throughout, tibia uniformly convex   


7. Male, parasitic vs non-parasitic

21Non-parasitic, common, in most but not all species the outer surface of the hind tibia has longer hairs along the front and rear edges with a region of bare or much shorter and less dense hairs in the center, in cross-section, this face also often flattened or deformed slightly from bi-lateral symmetry, the thickest portion usually shifted towards the front edge, fervidus and pensylvanicus are the main exceptions, having short uniform black hairs throughout, but tibia is thicker towards the front edge and underside of segment exceptionally flat, ocelli can be below the level of the eyes or if at the level of the eyes the lateral ocelli are equally distant between the eye and rear head margin or closer to the rear margin, warning, a few species do have ocelli clearly closer to the eye    2Parasitic, relatively rare to uncommon, outer surface of hind tibia uniformly hairy in density and hair length, hairs may be long or short, shape in cross-section is symmetrical, gently rounded with thickest portion running along center or only very slightly towards the front edge of the leg, ocelli always at level with the tops of the eyes, lateral ocelli always much nearer to eye than to rear margin of head   


8. Thorax, scutum, color of hairs on REAR HALF of plate

55Black    22Light    55Light and dark hairs mixed or in patches   



9. Thorax, scutellum, color of hairs

30Black    50Light    43Light and dark hairs mixed or in patches   



10. Thorax, below base of front wing, hair color

35Black, though usually with a small amount of yellow hair at the very top, covering not more than about 1/4 of segment    53Light    41Light and dark hairs mixed or in patches   



11. Abdomen, T1, hair color, not counting the hairs present on the anterior portion of the segment that faces the propodeum

23All black    50All yellow or off-white    29Light and dark hairs mixed or in patches    16With strong rust, brown, orange, red HIGHLIGHTS or all orange   




12. Abdomen, T2, hair color

26All black    43All yellow or off-white    32Light and dark hairs mixed or in patches    33With strong rust, brown, orange, red HIGHLIGHTS or all orange   




13. Abdomen, T3, hair color

39All black    30All yellow or off-white    29Light and dark hairs mixed or in patches    36With strong rust, brown, orange, red HIGHLIGHTS or all orange   




14. Abdomen, T4, hair color

2All PURE WHITE, NOT light yellow    34All black    43All yellow or off-white    41Light and dark hairs mixed or in patches    30With strong rust, brown, orange, red HIGHLIGHTS or all orange   





15. Abdomen, T5, hair color

5All PURE WHITE, NOT light yellow    55All black    25All yellow or off-white    37Light and dark hairs mixed or in patches    17With strong rust, brown, orange, red HIGHLIGHTS or all orange   





16. Head, malar space, the space between mid-point of attachment of mandible and very bottom of eye compared to width of base of mandible

45Clearly longer    28Clearly shorter    42Roughly equal   



17. Head, long hairs located just above antennae - Note that there is usually a fuzz of shorter, highly branched hairs that are often yellow, at the base of the longer hairs, these short hairs should be ignored

32Black    57Both light and dark hairs    44Light   



18. Head, color of hairs just behind ocelli

26Black    57Both light and dark hairs    49Light   



19. Head, ocelli, position relative to imaginary line across tops of eyes

60About right on the line    18Distinctly below   


20. Subgenus

3Bombias    6Bombus    12Cullumanobombus    4Psithyrus    30Pyrobombus    3Subterraneobombus    9Thoracobombus