The poster is now a feature of our Bumblebees page, along with some other information.
Omitted are common names. There are common names out there, but they can be confusing in a different way and we generally either adopt our own or abbreviate the scientific name, like "Vos" for Bombus vosnesenskii.
Bumblebee i.d. is not always easy nor certain. The only certainty is that the more one watches the more one sees.
Here are some hints on telling gender.
Males are different in appearance and habit in several ways.
1) Pollen basket. If the bumblebee has a blob of pollen on the hind leg, the bee is female. Even if not laden with pollen, the female hind femur is wider. The males may have pollen on his body, but it is haphazard.
2) Flower habits. Males spend much more time drinking nectar and less time gathering pollen -- only enough to feed themselves. Some flowers may draw mostly male bees, because they only produce nectar, or mostly female because they mostly produce pollen. Some flowers draw everyone.
3) Timing. Males show up at the end of a nest cycle, never in early spring. First a few queens show up preparing the new nest, then the female workers, then the males and the new queens.
4) Appearance. Males have longer antenna and a longer body, an extra segment each. They typically have more yellow, although it may be a little or a lot more depending on the species.
5) Sting. Only females can sting, (and they can sting more than once, the stinger is unbarbed). If you are very confident, you can test gender by hand-collecting a male. If you get stung it was not a male.
|B. californicus (fervidus) female|
|Bombus californicus (fervidus) male|
|B. vosnesensikii male|
|B. vosnesenskii female|
Now as we head into fall, field study slows hugely with most bumblebees closing camp and dying or (if new queens) headed to ground until spring. Mid-September and we have seen a few fat new queen vos, laden with fluids and calories, and a few workers of a couple of tenacious fall species are still out there. In the meantime, over the next few months we will sort through photos and observations and work on both this and other pages about our native pollinators.
Bumble Bees of North America, Paul Williams et al, 2014
Bumblebees of the Western United States, Jonathon Koch et al, 2012 (PDF available)
Xerces Society bumblebee i.d. http://www.xerces.org/bumble-bee-identification/
Xerces Society, bumblebeewatch.org