The Yellow-faced bumble bee, Bombus vosnesenskii, is a common bumble bee on the west side of Washington state and appears to be spreading into the eastern portion. There is some speculation that the drastic decline in numbers of the Western bumble bee Bombus occidentalis, during the 1990s created an opportunity for expansion of the Yellow-faced bumble bee.
Please reference the Embedded Range Maps page to better interpret
# of observations per ecoregion.
Field ID tips
The Yellow-faced bumble bee is a species that can be easily recognized once one has encountered them in the field. They have colonies that may contain upwards of 1,000 individuals, in contrast to most bumble bee species which have totals more in the 300-500 range.
When you encounter B. vosnesenskii you rarely just find a single individual. More often they will be numerous in the area. With their bright black coat and the distinctive and strongly contrasting yellow on the head, front of thorax (scutum) and most eye catching, on T4, they can be identified with relative confidence. Their fur is relatively even, giving them a well groomed appearance.
Similar species include the California bumble bee, Bombus californicus and the Obscure bumble bee, Bombus caliginosus.
The California bumble bee lacks yellow on the face.
The Obscure bumble bee is a trickier identification challenge. The color patterns are similar, with yellow on face, front of thorax and T4. The fur on the Obscure bumble bee is less even and more shaggy. A definitive field mark is on the underside of the abdomen where the Obscure bumble bee shows white hairs.
An easier photo might be capturing the face to be able to discern if the individual has a long or short cheek/facial structure. Bombus caliginosis has a long cheek and therefor a longer face relative to Bombus vosnesenskii who has a much shorter cheek length and a shorter face.