Eusocial: a form of insect society characterized by specialization of tasks and cooperative care of the young; socially highly organized. Queen substance: a pheromone secreted by queen bees and given to worker bees to prevent them from producing more queens.
Bumble Bees
A bumble bee (Bombus spp.) in a thistle (Cirsium spp.) at the Rancho Santa Ana Botanic Garden in California. Photo copyright Hartmut Wisch.
Bombus spp.
Description:Bumble bee species are large and very hairy. They are generally black and yellow but often have white or orange bands. They range in size between 3/8 and 3/4 inch long.
Life History:Bumble bees are social bees and have annual nests, often found in old rodent burrows but also in compost and wood piles. A queen will emerge from hibernation in early spring and start her own colony. Worker bees develop first, followed by males and new queens towards the end of summer. A bumble bee nest often contains between 300 and 500 individuals. New mated queens will hibernate in the ground over winter; workers, males, and the old queen die in the fall. Bumble bees eat only nectar and pollen and do not produce large amounts of honey.
Habitat:Bumble bees nest in open fields and woods.
Distribution:Bumble bees are found throughout North America.
Status:This species is declining across its range. Major threats include the spread of pests and diseases by the commercial bee industry, other pests and diseases, habitat destruction, pesticides, invasive species, and climate change.
Resources: Stinging Insects: Bumble Bees (K. Gardner, C. Klass, and N. Calderone, Cornell University Master Beekeeper Program)
A bumble bee (Bombus ternarius) in Aroostook County, Maine. Photo copyright Beatriz Moisset.
Over 50 species of bumble bees or humble bees (Bombus spp.), named for the humming sound they make while flying, occur throughout North America. These bees are large and robust, and are generally black and yellow often with white or orange bands. They are covered in branched hairs that pick up and transfer pollen. Female bumble bees have pollen baskets or corbiculae (cor-bic-yoo-lee, Listen to Merriam-Webster's pronunciation)- a broad concave shiny segment rimmed with long hairs and found on the back legs (click here to learn more about bee anatomy). The pollen baskets are used to carry pollen back to the nest. Additionally, they have relatively long mouth parts and are able to pollinate plants with deep nectaries, such as the blueberry (Vaccinium spp.). Bumble bees engage in a behavior called sonication, or buzz pollination. The bee places the anther in its jaw and vibrates each flower with its flight muscles, causing pollen to be dislodged. Tomatoes (Lycopersicon spp., syn. Solanum spp.) require buzz-pollination and bumble bees are important pollinators of this crop.
Bumble bees are generalist foragers and do not rely on one particular flower type. They are important pollinators of several wild flowering plants and crops like blueberry, tomato, eggplant (Solanum melongena), and pepper (Capsicum spp.), which is also a member of the Solanaceae family). They are also effective pollinators of some orchard crops like almonds (Prunus dulcis, syn. Amygdalus dulcis), apples (Malus domestica), and cherries (Prunus spp.). These bees are even considered better pollinators than honey bees (Apis mellifera) in some instances because bumble bees can fly during rainy, cool, cloudy, and windy weather and they have longer tongues than honey bees so they can pollinate flowers with long, narrow corollas or flowers. In North America, bumble bees are most important as pollinators of greenhouse crops. Bumble bees do not fly against windows like other bees and require smaller hives than honey bees. Often times they achieve close to a 100% pollination rate with tomatoes in greenhouses. Two species that have been domesticated for use in agriculture are the western bumble bee (Bombus occidentalis) in western North America and the eastern bumble bee (Bombus impatiens) in eastern North America. Two other bumble bee species that are important pollinators are the American bumble bee (Bombus pensylvanicus) and the buff-tailed bumble bee (Bombus terrestris).
A list of plants pollinated by bumble bees is hosted by the University of Wisconsin online at The Wisconsin Bumble Bee: Pollination (Paul H. Oliphant, University of Wisconsin).
Bumble bees are social bees. This means that they live colonially in hives or in bee communities. In contrast, non-social or solitary bees usually build and live in individual nests rather than in a hive or with a colony of bees.
Western Bumble Bee
Bombus occidentalis
Description:The western bumble bee has several color variations. One variant found from northern California, north to British Columbia and east to southwest Saskatchewan and to Montana has yellow hair on the front part of its thorax. The abdominal segments have black hair, with the lower abdomen being whitish colored. The head is entirely black. Another color variant occurs along the central coast in California and differs from the first in that it has yellow hairs on the sides of the abdomen and reddish brown hair lower on the abdomen. The third common variant occurs in the Rocky Mountains to Alaska and differs from the first in that it has yellow hairs behind the wings and in the middle of the abdomen. In all variants, males and females have similar coloring except that males have pale yellowish hair on the front of the face and the top of the head, with a few black hairs on the sides.
Distribution:Prior to the 1990's, the western bumble bee was common throughout the western coast of North America, from Alaska to central California and east to northern Nevada, Arizona, and New Mexico. The bees have undergone a dramatic decline and can currently be found in the northern and eastern parts of their historic range. Populations from southern British Columbia to central California have nearly disappeared.
Status:This species is declining rapidly across its range. The principal cause of the decline is believed to be the introduction of exotic disease organisms and pathogens from commercial beekeeping. Other threats include habitat loss and extensive pesticide use.
Subgenus Bombus Latreille, 1802 (Apidae: Apinae: Bombini) (Thorp, R. W., and M. D. Shepherd. 2005. Profile: Subgenus Bombus. In Shepherd, M. D., D. M. Vaughan, and S. H. Black (Eds). Red List of Pollinator Insects of North America. CD-ROM Version 1 (May 2005). Portland, OR: The Xerces Society for Invertebrate Conservation.)
The NBII Program is administered by the Biological Informatics Office of the U.S. Geological Survey
