Learn About Bumble Bees

All bumble bees belong to the genus Bombus within the family Apidae. The family Apidae includes the well-known honey bees and bumble bees, as well as carpenter bees, cuckoo bees, digger bees, stingless bees, and orchid bees. Bumble bees are important pollinators of wild flowering plants and crops. As generalist foragers, they do not depend on any one flower type. However, some plants do rely on bumble bees to achieve pollination. Loss of bumble bees can have far ranging ecological impacts due to their role as pollinators. In Britain and the Netherlands, where multiple bumble bee and other bee species have gone extinct, there is evidence of decline in the abundances of insect pollinated plants. Bumble bees are also excellent pollinators of many crops.

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Life Cycle

Bumble bees are the only bees native to North America that are truly social. They live in colonies, have different divisions of labor or castes, and have overlapping generations, usually with multiple broods throughout the spring, summer, and fall. However, unlike the non-native, European honey bees, the bumble bee colony has an annual life cycle. At the end of the summer the foundress queen, her workers and male offspring will all die; only the newly emerged, fertilized queens (gynes) survive to hibernate through the winter. In the spring, she will found a new nest that eventually may grow, depending on the species and available resources, to 50 – 500 individuals.

Bumble bees need a cavity in which to build their nest. The queens are opportunists, looking for any suitably sized cavity. Sometimes this is above ground, such as in hollow trees, abandoned bird nests, rock walls, or under a tussock of grass, but they mostly nest underground. An abandoned rodent hole is a favorite, as this space is warm and already lined with fur. The queen creates the first few brood cells from wax, and then provisions them with pollen and nectar and lays eggs. It will take four to five weeks for the first eggs she lays to emerge as adult bees; these bees become workers, taking on the tasks of foraging and helping the queen tend the growing number of brood cells. Depending on their role in the nest, workers may live for one to two months, by which time there will be more workers to replace them. The queen will continue to lay eggs, and the colony will grow steadily through the summer. At the end of summer, new queens and drones will emerge and mate. Because bumble bees have an annual life cycle, and generally only occupy nest sites for one year. Repeated use of the same nest site would happen only by chance, as overwintering queens do not spend the winter in the nest they were born. Because of this, we encourage folks that find nest sites near their home to try to make space for the bumble bees during the season, rather than attempt to move or exterminate them.

Understanding the life cycle of a typical bumble bee colony is the first step in understanding their unique habitat needs. Illustration by David Wysotski, Allure Illustration.

Lifecycle diagram illustrated by David Wysotski

 

1. A queen emerges from hibernation in spring and finds a nest site, such as an abandoned rodent burrow.

2. She creates wax pots to hold nectar and pollen, in which she lays and incubates her eggs.

3. When her daughters emerge as adults, they take over foraging and other duties.

4. In autumn the colony produces new queens and male bees, who leave to find mates. Newly mated queens hibernate and the rest of the bees die.

 

Foraging

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A closeup of the pollen basket. Photo by Beatriz Moisset [CC BY-SA 2.5]

Bumble bees are generalist feeders, often the first bees active in late winter (February) and the last in fall (November). Since they are active for so many months, they must be able to forage on a wide range of plant species in a wide range of weather conditions to support a colony. Early season, and late season resources are critical, as these are sensitive times of the year for successful establishment, and reproduction. Some individual bees in the colony choose to forage exclusively on a single species or a limited range of related plant species, effectively becoming specialist foragers. When foraging, the female bumble bee carries pollen in a concave, hairless area surrounded by stiff hairs on her rear legs, known as the pollen basket or corbicula. This basket can be seen clearly when it is empty and, when full, the pollen ball pressed into it is obvious.

Pollination

Bumble bees are able to fly in cooler temperatures and lower light levels than many other bees, and they perform a behavior called “buzz pollination,” in which the bee grabs the pollen producing structure of the flower in her jaws and vibrates her wing musculature causing vibrations that dislodge pollen that would have otherwise remained trapped in the flower’s anthers. Some plants, including tomatoes, peppers, and cranberries, benefit significantly from buzz pollination.

Bumble bees do make a small amount of honey, just enough to feed the colony for a couple of days during bad weather. This differs from European honey bees, who make large amounts of honey so the entire colony can survive the winter. Since newly mated bumble bee queens hibernate, they do not need the vast quantity of honey found in honey bee hives.

VIDEO: Vibrating Bumblebee Unlocks a Flower’s Hidden Treasure

Bumble Bee Identification

Bumble bees (Bombus spp.) have stout, hairy, robust bodies – usually with black, yellow, and/or red coloration. Bumble bees are variable in size and color patterns, even within a single species, which can make identification challenging. While color variation makes identification difficult, the coloration and pattern of stripes on the abdomen and thorax are often used to distinguish one bumble bee species from another – although for some species morphological features need to be observed. While bumble bees are distinct from most other bee species, there are some confusing look-alikes. Below are some resources to help you get started.

Bumble Bees Vs. Honey Bees

The European honeybee (Apis mellifera) is typically half to one-third the size of most bumble bees, with a slender, narrow body and mostly hairless abdomen with alternating black and honey-colored stripes.

Bumble Bees Vs. Carpenter Bees

In areas where both carpenter bees (genus Xyloclopa) and bumble bees are present it may be difficult to distinguish between them when in flight. Upon closer inspection however you’ll notice some key differences. On carpenter bees the upper surface of their abdomen is hairless and usually shiny black (depending on the species and sex), while bumble bees almost always have a hairy abdomen, usually with black, yellow, and/or red stripes. Another difference you may observe is that carpenter bees carry the pollen on their hind legs as a dry powder, while bumble bees carry their pollen moistened with nectar in specialized pollen baskets called corbicula.

Identification Guides

Register for Bumble Bee Watch, Use the Interactive ID Guide!

Bumble Bee Watch allows users to upload photo’s, tag location data, and use tools to ID species. These sightings are then verified by an expert and used to to track and conserve North America’s bumble bees. Read more.

Xerces Pocket ID Guides

Pocket ID guides are available for the following species: rusty-patched bumble bee. yellowbanded bumble bee. western bumble bee. folding instructions.

Streamlined Bee Monitoring Protocol

This guideline addresses basic knowledge for making identifications, protocols on how and when to monitor, and sample data sheets for recording observations. Read more.

Bumble Bees of North America

A comprehensive resource, Bumble Bees of North America is authored by Xerces Society collaborators and Bumblebee Specialist Group members: Paul Williams, Robbin Thorp, Leif Richardson, and Sheila Colla, this illustrated color guide will enable you to identify bumble bees encountered throughout the US and Canada.

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Learn About Bumble Bees
IUCN Bumblebee Specialist Group


Working with experts in the IUCN Bumblebee Specialist Group, the Xerces Society has completed research to better understand the extinction risk of all North American bumble bees and has found that more than one-quarter of North America’s bumble bee fauna are at risk of extinction. Learn more about bumble bee species at risk in the US and Canada.

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Contribute your local bumble bee sightings to Bumble Bee Watch!. Learn more.

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