The Black tail bumble bee, Bombus melanopygus, can be encountered in many areas around Washington state: Lowlands like Tumwater on the west side, in the mountains and over across the top of the state and beyond.
When I first started taking pictures of bumbles this species was one of the first I submitted to Bumble Bee Watch. It was also the species that taught me the bumble bee term “cloudy“. Cloudy is the term to describe bumble patterns that have a mixture of black and yellow hairs. On the Black tail bumble bee, the area in front of the wings (scutum) and behind the head is such a mixture of black and yellow. And on the Black tail bumble that cloudiness is very obvious.
Field ID tips
Abdomen pattern is similar in many respects to the Hunt bumble bee, with the big difference at T4.
The Black tail bumble bee
- Anterior thorax = cloudy (area in front of wings)
- T1 = yellow
- T2 = orange
- T3 = orange
- T4 = black with some white hairs
- T5 = black
T4 is black with some white hairs rather than cloudy because the white hairs are in a distinctive line rather than mixed in among the black hairs.
Species that could cause confusion include:
- the Hunt bumble bee (t4 is yellow)
- the Vancouver bumble bee (inverted triangle on scutellum, range)
- a habitat restricted high country specialist, the Forest bumble bee (shows a yellow, NOT CLOUDY, scutum [front of thorax]
- and the bane, oops, challenge for all western bumble bee enthusiasts, the Red-belted bumble bee.
My experience has been that the Black tail bumble bee is pretty distinctive most of the time, leading to confident field identification.