Creature Feature: Yellow-faced Bumble Bee

These pollinators may be small, but they are bee-yond important to the ecosystem.

We are in the height of California wildflower season, and the beauty that surrounds us is breathtaking. But behind all those stunning blooms are the inconspicuous pollinators that make wildflower season possible. Bees, butterflies, insects, and hummingbirds flit from flower to flower as they feed on nutritious plant nectar, picking up and distributing bits of pollen along the way, a process necessary for plant reproduction. With all the flowers blooming this season, it couldn’t be a more fitting time to learn about one of our native pollinators that helps make verdant springs possible: the yellow-faced bumble bee.

The yellow-faced bumble bee (Bombus vosnesenksii) is a species of bumblebee in the family Apidae that is common in the San Francisco Bay Area. The yellow-faced bumble bee can be found along the west coast of North America, as far north as British Columbia and as far south as Baja California. They can often be found visiting their favorite native flower species such as lupine, plume thistle, wild buckwheat, phacelia, clarkia, and ericameria. 

Given that there are 1,600 native bee species in California alone, it can be difficult to identify the yellow-faced bumble bee among other bee species. To differentiate bumble bees from other types of bees, look for their fuzzy bums! Unlike carpenter bees, bumble bees have fuzzy abdomens. Bumble bees are also larger, plumper, and fuzzier than their honey bee cousins. You can even tell different species of bumble bees apart by carefully studying the patterns of their fuzz — check out Bumble Bee Watch for a full identification guide. The yellow-faced bumble bee, as the name suggests, has a pale yellow face, a partially yellow thorax (middle body section), and a black body with a small patch of yellow on the lower abdomen. Additionally, yellow-faced bumble bees have a body part called a corbicula, a formation of hair on the bee’s hind legs that functions as a basket for carrying pollen. Like honey bees, bumble bees are not very aggressive and will only sting when they or their colony is threatened. However, while honey bee stingers have barbs that latch onto their victim and detach the stinger from their abdomens, bumble bee stingers have no barbs, and thus they can sting multiple times. Another surprising fact is that bees have tongues — you may be lucky enough to see the yellow-faced bumble bee’s tongue while they visit a flower, lapping up the sugary plant nectar.

At this time of year, yellow-faced bumble bees are taking advantage of spring’s floral bounty by foraging nectar and pollen to support the queen’s larvae. In autumn, queens will focus on reproduction while workers will focus on collecting nectar and pollen. During this period of time, the colony will include up to 300 worker yellow-faced bumble bees. However, by the end of autumn, the worker yellow-faced bumble bees will complete their life cycle and reach the end of their lifespan. A new generation of queens will be born, mate with male yellow-faced bumble bees (called ‘drones’), and go into hibernation. Early next spring, these queens will emerge from hibernation and search for an abandoned underground rodent den to use as a nest site for the colonies they will create in the coming year. Yellow-faced bumble bee queens forage for food until the first generation of worker bees is born, and the process begins anew.

The yellow-faced bumble bee is not currently an at-risk species, and in fact, populations have grown in recent years. However, the same cannot be said for many other native species of bumble bee, some of which have experienced great population decline due to rising atmospheric temperatures, drought, habitat destruction, and pesticide use. In fact, the yellow-faced bumble bee’s population growth is likely because they filled the ecological void left by disappearing bumble bee species or outcompeted them for resources. Though the yellow-faced bumble bee’s success may seem positive, it is actually a marker of declining biodiversity at the hands of humans. 

Plant life as we know it depends on these humble creatures, and so do we. The yellow-faced bumble bee is an extremely important pollinator for agricultural crops, especially tomatoes. In fact, many of the foods we eat would not grow without bumble bees. Preserving our native bee species, including the incredible yellow-faced bumble bee, is necessary for not only the health of the ecosystem, but also the health of humanity.

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