Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.
Field ID tips
We have three species of cuckoo bumbles in Washington state.
Out of the three cuckoo queens, within Washington, only the Indiscriminate cuckoo bumble bee will show a black notch on T4.
At least in Washington, Fernald cuckoo bumble bees B. fernaldae and Indiscriminate cuckoo bumble bee. B. insularis are somewhat easy to distinguish between. As seen in the picture above and below, the Indiscriminate cuckoo has black up the center of tergites T3, T4 and T5 that break up the yellow bands. The Fernald cuckoo bumble bee will have a continuous yellow band on T4 (no black interruption).
The Suckley cuckoo bumblee bee queen also has a solid yellow T4, so the presence of black on T4 is a strong indicator what you have is Bombus insularis. The key distinguishing feature for separating the Indiscriminate cuckoo bumble bee, B. insularis from Suckley cuckoo bumble bee, B. suckleyi, according to the key in Bumble Bees of the Western United States, by Koch, et al, 2012, is the color of the hairs on the back of the head (Occiput). If the hairs on the back of the head are predominantly black it is B. suckleyi.
Both B. flavidus / fernaldae and B. insularis have mainly yellows hairs on the back of their heads. This is important to remember, as far as capturing the key elements needed for photographic identification.