Bumble Bees

By Kate Redmond

There are more than 4,000 species of native bees in North America, and they pollinate native plants, ornamentals, and farm crops, alike. Native bees are considered “keystone species” because of the profound effect they have on their ecosystems, tending the plants that produce the fruits, seeds, nuts, and leaves that feed and shelter birds and other animals. Imagine what the landscape would look like if the pollinators disappeared!

Of the 400 species of native bees in Wisconsin, the 15 species of bumble bees are the most conspicuous, especially when large queen bumble bees are foraging on early spring wildflowers. Bumble bees live communally, and these queens care for the first crop of workers that will take over defense, foraging, and the maintenance of the colony’s nest and nursery. Other pollinators include butterflies, moths, wasps, beetles, flies, ants, and even hummingbirds.

1. For a long time (and despite what their eyes told them), scientists thought that it was mathematically impossible for bumble bees to fly. Bumble bees’ bodies are plump, and their wings are very small for their bulk. Researchers finally discovered the trick -- bumble bees can fly because instead to flapping their wings up and down, the bees “row” from front to rear with their wings.
2. Only the queen bumble bee survives the winter. She must emerge early to claim the limited available nest sites, but her extra-hairy body is well insulated against the chill of April and May. Some entomologists refer to the bumblebee as an essentially warm-blooded bee.
3. As a group, bumble bees are northern bees, tough enough to survive above the Arctic Circle. They thermoregulate, producing heat by internally “shivering” their flight muscles without beating their wings, and their thick, insulating hairs help to retain that heat. They need an internal temperature of 86 degrees before they can fly. In chilly weather, queen bumble bees use the same isometric trick to incubate their eggs, warming the thorax and then sending heat to a bare spot on the underside of the abdomen, similar to a bird’s “brood patch.”  
4. Different species of bumble bees have tongues of different lengths, and this governs their flower choices. They’re also “muscly” pollinators that are able to force their way into flowers that other bees can’t, like turtlehead and legumes. Sometimes they cheat, and chew their way in at the base of a flower.
5. A bumble bee’s buzz is produced by the vibrations of its flight muscles as it flies
6. Bumble bees can “Buzz pollinate” (honey bees can’t), which makes them the ideal pollinators for tomato, cranberry and blueberry flowers. They approach a downward-facing flower, grab it, and give a little shiver while simultaneously buzzing at approximately “Middle C.” The 400Hz vibration loosens the pollen grains and sends them raining down onto the bee’s hairy body, where she grooms the pollen into her pollen sacs. One researcher calls them “living tuning forks.” For a video, click here.
7. It’s all done with magnets. As a bee flies through the air, the resistance/friction it encounters causes a small, positive electric charge to build up on its body. When it lands on a flower, the pollen grains, which have a slight negative charge, are attracted to the bee and will attach to its hairs even if the bee doesn’t actually brush against them.
8. There are 49 species of bumble bee nationwide.
9. Bumble bees provide vital “Ecosystem Services.” They pollinate many wildflowers and wild fruits and berries. Although bumble bees themselves are generalists, some of the flowers they pollinate can’t be accessed by other bees (bumble bees are the only bees that can pollinate red clover), so their actions affect ecosystem diversity and integrity. The resulting plants, fruits and seeds -- and the invertebrates that are attracted to the plants (and the bumble bees themselves) -- are eaten by wildlife. 
10. Bumble bees pollinate 15% of U.S. crops (they fly in cooler, damper, and darker weather than honeybees do), and they are now raised commercially and moved around internationally, just like honey bees. 

But, there are some NOT-SO-FUN FACTS about bumblebees, too.

Like honey bees, native bees are disappearing, due to: 

• diseases and parasites carried by domestic bees (including imported, commercial bumblebees) that spread to wild bees; 
• air pollution (a University of Virginia study showed that gasses from cars bond with the scent molecules of flowers and make it harder for pollinators to “follow their noses.”);  
• some of the bumble bee colonies that are put to work pollinating crops have been removed from the wild; 
• climate change (some may like it hot, but not bumble bees); 
• pesticide use; 
• habitat loss; and 
• habitat fragmentation. The current trend toward “agricultural intensification” has resulted in the removal of fence rows and natural borders, depriving bees (and birds) of resting and nesting places, feeding diversity, and nectar corridors.

We can support bees by planting clumps of bee-friendly, native plants that have different heights, shapes, and colors, and that bloom throughout the growing seasons -- from pussy willows and basswood to bergamot and milkweed to goldenrod and aster. Plant enough, and you’ve created a habitat that will make butterflies and birds happy, too.
 
Most native bees are solitary – they do not have large, communal hives. Make a Bee Hotel to encourage them. Click here to see two plans for DIY bee shelters; lots more are available online, and garden stores sell them.

Many solitary native bees nest in the ground or in dead trees. Can you spare a patch of lawn? Leave a dead tree standing? Rototill or spade up a small area on the lawn’s edge and see what comes in.

Try your hand at bumble bee identification:
Wisconsin Pollinators

Be a Citizen Scientist. Observe bumble bees in the field and report your sightings to Wisconsin’s Bumble Bee Brigade. 

For more information about bees: 

Bumble Bees of Wisconsin