This key is for the females of the genus Bombus known from The Evergreen State College campus, in Olympia, Washington. Click here to confirm that your specimen is a female Bombus. Click here to learn more about variation in Bombus morphology within a species.
This key is based on Thorp et al. (1983). All micrographs were taken by the web site author, Matthew P. Kweskin.
1a. Malar space longer than wide....1.1
1b. Malar space as long as, or shorter than wide....1.2
| 1.1 | 1.2 |
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1.1a. Gastral tergum 4 with orange hair, others mostly black. Scutellum with black hair, occasionally with yellow intermixed laterally.....B. californicus
1.1b. Gastral terga 3 and 4 black; scutum anterior to tegulae and scutellum usually with a mixture of black and yellow pile; .....1.1.2
| B. californicus | 1.1.2 | |
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1.1.2a.Fifth and sixth gastral terga with brownish red hairs and the sixth gastral sternum (the hypopygium) lacking a median carina.....B. sitkensis
1.1.2b.The fifth and sixth gastral terga with mostly dark hair; the hypopygium sometimes with a median carina.....B. flavifrons
| B. sitkensis | B. flavifrons |
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| T5 and 6 with brownish red hairs | T5 and 6 with mostly dark hairs |
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| Hypopygium without ridge | Hypopygium sometimes with ridge |
1.2a. Length of flagellomere 1 equal to 3; apical portion of gastral tergum 4 and all of terga 5 and 6 with whitish hair, other terga black; malar space wider than long..... B. occidentalis
1.2b. Flagellomere 1 longer than 3; terga 4, 5 and 6 without white hair. [If gastral terga 4, 5, or 6 have light hair, then terga 1, 2, and 3 are not all black (B. mixtus), or face with all yellow hair (B. vosnesenskii)]; malar space as or longer than wide.....1.2.2
| B. occidentalis | 1.2.2 |
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| Terga 4, 5, and 6 with whitish hair. |
1.2.2a. Gastral tergum 4 with black hair laterally and basally, reddish or brownish white medioapicaly; terga 2 with yellow hair, at least centrally; terga 5 and 6 with reddish or brownish white hair.....B. mixtus
1.2.2b. Gastral tergum 4 with hair all yellow or all black; terga 2 with predominantly red or black hair; terga 5 and 6 with mostly black hair.....1.2.2.2
| B. mixtus | 1.2.2.2 | |
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| Tergum 4 with black hair laterally and basally; reddish or brownish white hair medioapicaly; terga 2 with yellow hair, at least centrally. | Tergum 4 with hair all yellow or all black; terga 2 with predominantly red or black hair. | |
1.2.2.2a. Gastral terga 2 and 3 with red hair; pile of scutum anterior to tegulae and face yellow mixed with black.....B. melanopygus
1.2.2.2b. Gastral terga 2 and 3 with black hair; scutum anterior to tegulae and face with yellow pile.....B. vosnesenskii
| B. melanopygus | B. vosnesenskii |
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| Terga 2 and 3 with red hair. | Terga 2 and 3 with black hair. |
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| Scutum anterior to tegulae yellow mixed with black. | Scutum anterior to tegulae yellow. |
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| Face with yellow and black hair mixed. | Face with yellow hair. |
Page author: Matthew P. Kweskin
Last modified: 31 Mar 1997
For more information about this site, please contact John T. Longino longinoj@evergreen.edu