A photographic key based on color patterns for bumble bees in Washington state
This key may not work as well in other parts of the country
Some interpretive notes:
- Red is often short-hand for orange, in descriptions
- Light colored area may be either yellow or white on a given individual, e.g., Two form bumble bee.
- Golden refers to a deep rich yellow, e.g., Nevada bumble bee
- ID means the key has predicted a species based on previous questions
| Step | Description | Go to # | Comments or link to diagram or species |
| Female vs Cuckoo/male | |||
| 1 | Corbiculum / pollen basket present | 5 | Corbiculum defined |
| 1’ | Rearmost leg hairy/rounded | 2 | No pollen basket, see example |
| Cuckoo female vs all males | |||
| 2 (1) | Heavy bodied cuckoo female | 3 | What are cuckoo bumble bees? |
| 2’ | Male, any species | ID | No key provided at this time |
| Separating cuckoo queens | |||
| 3 (2) | T4 with black notch | ID | Indiscriminate cuckoo bumble, B. insularis |
| 3’ | T4 w/out black notch | 4 | |
| 4 (3’) | T4 yellow, T5 all black, occiput with yellow hairs | ID | Fernald cuckoo bumble bee, B. flavidus |
| 4’ | T5 with some yellow, black notch, occiput with predominately black hairs | ID | Suckley cuckoo bumble, B. suckleyi (very rare) |
| Starting all non-cuckoos | |||
| 5 (1) | White on either scutum (thorax front of wings) or T4+T5 | 6 | bumbles showing white |
| 5’ | No white areas as described above | 7 | |
| Bumbles showing white | |||
| 6 (5) | White scutum, golden abdomen | ID | White-shouldered bumble, B. appositus |
| 6’ | Scutum golden, T4 and T5 white | ID | Western bumble bee, B. occidentalis |
| Bumbles showing yellow | |||
| 7 (5’) | Bumble bee predominately yellow | 8 | Bumbles showing yellow males of several species may be yellow (e.g., flavifron, mixtus) check rearmost leg for pollen basket |
| 7’ | May show yellow but other colors also, may be striped | 9 | |
| Separating Yellow bumble from California bumble | |||
| 8 (7) | T1-T4 yellow, T5,T6 black | Yellow bumble bee, B. fervidus | |
| 8’ | Black wing band, T2 and T3 shows some black | California bumble bee, B. californicus | |
| Bees showing red on abdomen | |||
| 9 (7’) | Red on abdomen | 10 | Red on abdomen |
| 9’ | No red on abdomen | 21 | |
| Separating Reds into 2 subgroups | |||
| 10 (9) | Red on middle of abdomen | 11 | Example of Red on Middle |
| 10’ | Red at hind end of abdomen | 18 | Example of Red at hind end |
| Red on middle of abdomen group | |||
| 11 (10) | Scutum yellow, T1 and T2 yellow, T3 and T4 red/OJ, T5 black | ID | Central bumble bee, B. centralis |
| 11’ | Not as above | 12 | |
| 12 (11’) | Scutum cloudy, T1 and T2 yellow, T3 and T4 OJ/black, T5 black | ID | Yellow head bumble, B flavifrons red color morph |
| 12’ | Not as above | 13 | |
| 13 (12’) | T2 and T3 red/orange | 14 | |
| 13’ | T2 or T3 show red/orange | 17 | |
| 14 (13) | Scutum cloudy | 15 | |
| 14’ | Scutum yellow, no black hairs | 16 | |
| 15 (14) | Black inverted triangle on scutellum, range associated with San Juan Islands, often black notch on T2 | ID | Vancouver bumble bee, B. vancouverensis |
| 15’ | T1 yellow, T4 black w white hairs in line | ID | Black tail bumble bee, B. melanopygus |
| 16 (14’) | T4 yellow, dry eastern lowlands | ID | Hunt bumble, B. huntii |
| 16’ | T4 yellow, high elevations only | ID | Forest bumble, B. sylvicola |
| 17 (13’) | Scutum and scutellum both yellow, T2 usually shows at least some yellow small body size, very short face | ID | Red-belted bumble, B. rufocinctus |
| 17’ | Scutellum with black inverted triangle | ID | Two form bumble, B. bifarius (red morphs) |
| Red at hind end of abdomen Group | |||
| 18 (10’) | Scutum cloudy | 19 | |
| 18’ | Scutum yellow | 20 | |
| 19 (18) | T3 orange sometimes with black, T4 and T5 orange, distinct “red” tail | ID | Fuzzy-horned bumble, B. mixtus |
| 19’ | T3 black, T4 and T5 pale orange hairs, subtle | ID | Sitka bumble, B. sitkensis |
| 20 (18’) | T3 black | ID | Frigid bumble bee, B. frigidus |
| 20’ | T3 black and yellow | ID | High country bumble, B. kirbiellus red form |
| No Red on Abdomen | |||
| 21 (9’) | No red, yes stripes | 22 | See examples |
| 21’ | Hind end of abdomen black | 26 | See examples |
| Striped bumbles | |||
| 22 (21) | T1 and T4 white or yellow, inverted black triangle on scutellum | ID | Two form bumble, B. bifarius |
| 22’ | Not as above | 23 | |
| 23 (22’) | Face black, scutum and T4 yellow | ID | California bumble bee, B. californicus |
| 23’ | Face yellow | 24 | |
| 24 (23’) | T3 yellow | van Dyke bumble, B. vandykei | |
| 24’ | T3 black | 25 | |
| 25 (24’) | Stergites black, hair very even | ID | Yellow-faced bumble, B. vosnesenskii |
| 25’ | Stergites with white hairs, hair shaggy | ID | Obscure bumble bee, B. caliginosus |
| Bumbles w black end of abdomen | |||
| 26 | Thorax and T1 thru T4 yellow, T5 black, corbiculum present | ID | Yellow bumble, B. fervidus without pollen basket, may be a male |
| 26’ | Not as above | 27 | |
| 27 (26’) | T2 black | ID | Common eastern bumble, B. impatiens |
| 27’ | Not as above | 28 | |
| 28 (27’) | T3 golden or yellow | 29 | |
| 28’ | Not as above | 30 | |
| 29 (28’) | Black dot between wings | ID | Nevada bumble, B. nevadensis |
| 29’ | No black dot between wings | ID | Morrison bumble, B. morrisoni (very rare in WA) |
| 30 (28’) | Scutum cloudy, T1, T2 yellow, possibly with black notches | ID | Yellow head bumble bee, B. flavifrons |
| 30’ | Not as above | 31 | |
| 31 (30’) | T1 yellow, T2 with yellow or brown, relatively large bodied | ID | Brown-belted bumble, B. griseocollis |
| 31’ | T1, T2 yellow, medium to small body size | ID | Half-black bumble, B. vagans |