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Spring 2022

Behold the buzzy bumble bee

Bumble bees are native to California. Photo: UCANR
Bumble bees are native to California. Photo: UCANR
The European honeybee is a familiar sight, but did you know that there are 1,600 bees native to California? These bees look and act differently than honeybees in that they don't live together in hives and they don't make honey. Instead, native bees are solitary, live in wood nests, collect pollen for their young, and lay eggs. These bees come in a variety of shapes, sizes, and markings. Among them are California's beloved bumble bees (Bombus californicus), large, hairy bees with the familiar black and yellow bands. Bumble bees aren't quite as zippy as some other bees. Instead, they float relatively slowly between flowers. Interestingly, they are the only native bees that have some habits in common with honeybees. For instance, they live in colonies and have a queen and share jobs. However, unlike honeybees, a bumble bee colony only lasts one year.

Bumble bees are buzz pollinators

Like other native bees, bumble bees can grab onto a flower and move their flight muscles so rapidly that the vibration to the flower's anthers causes pollen to be dislodged. This is called buzz pollination. About 6 percent of flowering plants need buzz pollination. Bumble bees provide this service to many agricultural crops, including tomatoes, cherries, apples, avocados, alfalfa, blueberries, and blackberries. Unfortunately, honeybees are unable to buzz pollinate.

Unlike honeybees, California's native bumble bees can perform buzz pollination. Photo: Barmalyanich, Pixabay
Unlike honeybees, California's native bumble bees can perform buzz pollination. Photo: Barmalyanich, Pixabay

Watch buzz pollination in action.

Decline in bumble bee populations

There are 40 bumble bee species in North America, and 26 are in California. The California bumble bee was the most common bumble bee in California until the 1990s when populations declined. There are many factors that may have contributed to this decline, including pesticides, loss of habitat, invasive species, and climate change.

Life cycle of a bumble bee

At the end of summer, queen bumble bees and all her workers and male offspring die and only the fertilized queens, called gynes, survive to hibernate through winter. Come spring, these survivors find a cavity to build new nests. Sometimes these nests are above ground in hollow trees or abandoned bird nests, but they are typically underground. Abandoned rodent holes are particularly attractive because the space is warm and lined with fur.

A bumble bee emerges from her colony and dines on a manzanita flower. Photo: Las Pilitas
A bumble bee emerges from her colony and dines on a manzanita flower. Photo: Las Pilitas
When the queens emerge, they need flowers to visit. They can often be seen feeding on early-blooming California native plants. If it's particularly cold, the queen bees use their flight muscles to raise their body temperature. Once the queen has eaten and has a full tank, she flies low over the ground in a zigzag pattern to find a new cavity for a nest. She creates a little pot of wax and saves a small mound of pollen as a food stash and then lays eggs and incubates them. When the larvae hatch, the queen bumble bee regurgitates food into the pot – sort of like how birds feed their babies. After about two weeks, the larvae chew their way and become the first worker bees.

Want to help a bumble bee? Plant manzanita.

Bumble bee queens must have access to food sources in late winter and early spring when they come out of hibernation. Without that and/or the ability to find a nest, they can't build colonies. One of the first plants used by these hard-working bees are California's beautiful manzanitas. There are over 100 species of manzanita (Arctostaphylos), from ground-huggers to trees. They are evergreen and often have attractive bark. Here's where you can find a manzanita that's right for your garden.