I find the Fuzzy-horned bumble bee, Bombus mixtus, to be a common species in Thurston County and much of the west side. It is also found in the north central of the state, and the mountainous areas in eastern Washington.
Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.
Field ID tips
The relatively bright red rear of the abdomen is a prominent field mark I see on this species. The abdomen feels three (3) toned. Yellow transitioning into black and then into orange.
- T1 = yellow
- T2 = yellow with some/ a lot of black possible
- T3 = black, possibly with some orange
- T4 = orange
- T5 = orange
My ID challenge with the Fuzzy-horned bumble bee, B. mixtus is that there are some other, less common species with similar color patterns, such as the Sikta bumble bee, the High country bumble bee and the Frigid bumble bee. Recognizing that an individual with red at the end of the abdomen is NOT mixtus is the larger challenge.
Let me restate: assume you are looking at a Fuzzy-horned bumble bee and then decide if one of the other species may be a better match.
Having said that, Sitka can be ruled out easily because the colors at the end of the abdomen are not as bright and often do not extend up to T3 or even the front portion of T4.
The other two are easily ruled out in most circumstances based on location. Those two species, are high alpine specialists and are not routinely encountered unless extremely lucky or on a targeted mission. A key field mark for separating Bombus mixtus from the other two is color of the scutum. The Fuzzy-horned bumble bee has a cloudy scutum (yellow with black hairs also). The scutum on both the High country bumble bee and the Frigid bumble bee is yellow.