Stop the presses! As of July 29, 2020 Washington state has a new bumble bee species. Genetic analysis has determined that the population of the Two form bumble bee, Bombus bifarius in British Columbia has been recognized as a new, separate species. This new species is the Vancouver bumble bee, Bombus vancouverensis. This includes the population located in the San Juan Islands. Ergo, we have a new species!
What is not clear is what the actual differences are between the Vancouver bumble bee and the Two form bumble bee. At first I (DJ) thought that the individuals showing red on T2 and T3 were vancouverensis and the ones with T2 and T3 black were bifarius. Now it appears separating the two species in Washington may be a bit more challenging. It appears that the two color morphs are subspecies of the same species (B. vancouverensis)
As I am interpreting (please correct me if you know better!) the colorful color morph found in the San Juans Islands is the Vancouver bumble bee subspecies Bombus vancouverensis vancouverensis, while the form that we knew in the eastern part of Washington as the Two Form Bumble bee (Bombus bifarius) is now the Vancouver bumble bee subspecies Bombus vancouverensis nearcticus. For more discussion on this taxonomic question, please refer to the Two Form bumble bee page.
For a more complete discussion on field identification of the Bombus vancouverensis nearcticus subspecies refer to the Two Form bumble bee page.
Field ID Tips
Range, range, range. As far as I am currently aware, within Washington state, the Vancouver bumble bee Bombus vancouverensis vancouverensis subspecies is restricted to the area around the San Juan Islands. It has a similar color pattern to the Two Form bumble bee. It shows an inverted black triangle on the scutellum. T1 & T4 are yellow. T2 and T3 show a lot of red. T2 may show a black notch.
The red morph of the Yellow head bumble bee, which is also located in the San Juans, is somewhat similar, but it show red on T3 and T4. The Yellow head bumble bee also lacks an inverted black triangle.
The Black tail bumble bee shows red in the middle of the abdomen. T4 is black with a white line of hairs, no inverted black triangle.