Two form bumble bee, Bombus bifarius

The Two form bumble bee is a small bodied species common on the east side of Washington state. It can be found on the west side as well, but seems to thrive on the east side. Note the black triangle pointed at the abdomen, on the backside of the thorax (scutellum).

There is some confusion after the Vancouver bumble bee, Bombus vancouverensis, was separated from Bombus bifarius as to how to separate them and where do the two species occur separately and where do they overlap. While I (DJ) first thought B. vancouverensis was the red form found in the San Juans Islands and up north in the central part of British Columbia, now it seems that it may not be a correlation between external colors and species distinction. More to come.

In the short term, I am leaving this as B. bifarius. This page may be updated as a better understanding of the differences between the two species.

Field ID tips

Identification of the Two form bumble bee, Bombus bifarius is fairly straight forward for the most common color morph in Washington. There is a black band between the wings and a black inverted triangle coming from that black band down to the abodomen.

The abdomen is distinctly striped:

  • T1 = yellow or white
  • T2 = black (maybe some red)
  • T3 = black (maybe some red)
  • T4 = yellow or white
  • T5 = black

Similar Species

The Red-belted bumble bee, B. rufocinctus, with its’ many color morphs can be confusing to separate. Red-belted lacks a black inverted triangle, and T2 should show some yellow.

The non-standard color morphs of B. bifarius all show the black inverted triangle below the black wing band. The abdomen however may have some or lots of red on T2 and/or T3.

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Washington's bumble bees

Bumble Bees of Washington State

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