Pollinator of the Week: Yellow-Faced Bumble Bee

Bombus vosnesenskii foraging on blanket flower in a Portland garden, July 2017.

This entry is from Isabella Messer an undergraduate horticulture major at Oregon State University.  It highlights one of the most common pollinators that we see in Portland area gardens.

Out of the twenty four different garden sites we visit, each month in Portland, we can count on one bumble bee being present in almost all of the gardens. This ubiquitous bee is Bombus vosnesenskii, otherwise known as the yellow faced bumble bee. With increasing evidence that some bumble bee populations are declining, Bombus vosnesenskii populations remains stable (1).

B. vosnesenskii is a very common bumble bee of increasing abundance across the western United States, although it ceases to be very common east of the Sierra Cascade Crest in California(2). B. vosnesenskii is most easily identified by the yellow hairs on the top of the head, on its face, on top of its thorax (middle body part), and as a yellow band at the base of their abdomen (bottom and biggest body part) (2). In terms of the flowers and plants that B. vosnesenskii likes to visit, they are broad generalists (3). This means that they like to visit a broad variety of plants. They are considered ‘medium tongue’ bees, which means that they can drink nectar from a wide array of flowers, with floral morphologies ranging from zinnias, to coneflowers to rhododendrons. Keep an eye out for their yellow heads the next time you are out in the garden and it is very likely you will come across one.

References:

1. Lozier, Jeffrey D., James P. Strange, Isaac J. Stewart, and Sydney A. Cameron. (2011). Patterns of range-wide genetic variation in six North American bumble bee (Apidae: Bombus) species. Molecular Ecology, volume 20(23), pp 4870-4888.
2. Koch, Jonathan, James Strange, and Paul Williams. Bumble Bees of the Western United States. US Forest Service and the Pollinator Partnership. PDF.
3. Tepedino, V.J., Laura C. Arneson, and Susan L. Durham. (2016). Pollen removal and deposition by pollen-and nectar collecting specialist and generalist bee visitors to iliamna bakeri(malvaceae). Journal of Pollination Ecology, volume 19(15). Pp 50-56.

Bombus vosnesenskii foraging on zinnia, in a Portland area garden, August 2017.