Two-spotted Bumble Bee

Pronunciation

How to pronounce Bombus bimaculatus: //ˈbɒm.bəs ˌbaɪ.məˈkjuː.lə.təs//

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Summary

The Two-spotted Bumble Bee (Bombus bimaculatus) is a stable and abundant pollinator found predominantly in the eastern United States and southeastern Canada, recognized for its two distinctive yellow markings on the abdomen, and plays a substantial role in pollination despite other bumble bee species experiencing declines.

Physical Characteristics

Females have a body length of 17-22 mm, workers range from 11-16 mm, and males are 13-14.5 mm. Females have extensive yellow on the second abdominal tergite (T2) that forms a deep 'U' shape, while the lateral portions are largely red.

Identification Tips

Workers resemble queens but are smaller; queens have a black face with a yellow triagular patch on the vertex. Queens are distinguished by a conspicuous circular black spot on the female scutum. Males have intermixed black and yellow hairs and can be recognized by black corners of their tergite 2 (T2).

Habitat

Mainly found in eastern temperate forest regions, coastal plains of the southeastern United States, eastern Boreal forests, and eastern Great Plains. Nests are usually underground in wooden areas and gardens, but can also be found in cavities or above ground.

Distribution

Eastern North America: from Ontario to Maine, south to Florida, and west to Mississippi.

Diet

Pollinates a wide variety of plants, favoring some species such as willow, plum, red clover, and mint. Known floral associations include Zenobia pulverulenta, Aquilegia species, and Mertensia species.

Life Cycle

Colony cycle is annual, with new colonies founded by mated queens in spring. Eggs hatch after four days, followed by a larval feeding stage of two weeks before pupation. Workers typically emerge in May, peak in July, and males emerge last in June.

Reproduction

Queens mate outside the nest, usually only once, but some may mate multiple times, leading to offspring with multiple paternity.

Predators

Predators include crab spiders, Florida black bears, ambush bugs, robber flies, dragonflies, assassin bugs, and certain wasps. They are ambushed by crab spiders at flowers and eaten by Florida black bears primarily in spring.

Ecosystem Role

Serves as an important pollinator in temperate forest regions, supporting diverse plant species due to their foraging efficiency even in sub-optimal weather.

Health Concerns

Only female bees can sting, primarily when defending nests. Reactions to stings are less common than honey bee allergies.

Evolution

Part of the subgenus Pyrobombus, closely related to B. monticola, B. sylvicola, and B. lapponicus. Often confused with B. impatiens and B. griseocollis due to similar coloration.

Similar Taxa

• Bombus impatiens
• Bombus griseocollis
• Bombus monticola
• Bombus sylvicola
• Bombus lapponicus

Misconceptions

Often referred to simply as the Twospotted Bumble Bee, the species name can be confused with the common name by not using hyphens that help clarify the naming conventions.

Tags

• Bumblebee
• Pollinator
• Eastern North America