Bombus

Taxonomy

Order: Hymenoptera
Family: Apidae
Subfamily: Apinae
Tribe: Bombini
Genus: Bombus Latreille, 1802
Common names: bumble bees or bumblebees

Background

Bumble bees are well known due to their bright colors, large body size, flower-visiting activity during daylight hours, and overall abundance. They are important pollinators of both crops and wildflowers. Bumble bee species are declining in Europe, North America, and Asia due to several factors, including loss of food plants and nesting sites, pesticide exposure, and pathogens.

How to separate from Asian giant hornet

  • Bumble bees are smaller than Asian giant hornets and have very stout and "fuzzy" bodies
  • Many common species are black with yellow markings
  • One common western species (B. huntii) is yellow and black with a patch of bright orange on the abdomen

Distribution

Bumble bees are typically found in temperate climates. They are most abundant and diverse in humid, cool sites rich in flowers, such as mountain meadows.

Bombus is found throughout North America where there are 43 species in the west, 24 species in the east, and 18 in the south (Thorp et al. 1983). A total of 260 species in 15 subgenera are found worldwide, including the Arctic (Williams 2021). Bombus species are only present in northern Africa and are not native to Australia, though they were introduced to Tasmania (Asher and Pickering 2017).

Distribution of Bombus by GBIF: https://www.gbif.org/species/1340278

Diagnostic characteristics

  • Bumble bees are generally heavy-bodied and very hairy.
  • They are larger and broader than honey bees, and the tip of their abdomen is more broadly rounded.
  • Body length 1.5–2.5cm (0.6–1.0 inches)
  • The body is generally black with broad bands of color on their abdomens.
  • They have long tongues to collect nectar.
  • Females collect pollen onto a flattened area on the hindtibia, called a corbicula.
  • Male Bombus do not have a corbicula.
  • Males also have 7-segmented abdomens instead of the six found in females.

Diversity

Worldwide there are about 260 species in 15 subgenera.

Host/prey associations

Most bumble bees build nests with a queen and workers. However, bumble bees in the subgenus Psithyrus, also known as cuckoo bumble bees, are brood parasites. Psithyrus females do not collect pollen themselves, but will enter a bumble bee colony and kill or subdue the queen. An invading female uses pheromones and physical attacks to force the workers of the colony she's entered to feed her and her young.

Nesting and general behavior

Mated, overwintered queens emerge from their hibernacula in very early to late spring, depending on the species. They then begin building nests and provisioning the cells with balls of pollen and nectar. Workers emerge in late spring to early summer after which they build in numbers and persist until late summer to late fall depending on the species. Most colonies have between 50 and 400 individuals. Many species nest underground, using old rodent burrows or similarly sheltered places; they actively avoid places that receive direct sunlight to avoid overheating. Other species make nests above ground in thick grass or tree holes. Virgin queens and males appear in summer to fall, depending on the species, and visit flowers at that time along with foraging workers. At the end of the season workers and males die and newly mated queens enter their hibernacula where they remain dormant until spring. In warm areas such as southern California and South Florida, bumble bees can be found flying even in mid-winter.

Known invasives

Four European species of Bombus have been introduced to Tasmania and New Zealand (Asher and Pickering 2017). The European species, Bombus impatiens, has been introduced into parts of the United States for blueberry pollination.

<p><em>Bombus affinis</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus fervidus</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus huntii</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus huntii</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus huntii</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus huntii</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus huntii</em>; photo by U.S. Fish and Wildlife Service, Flickr</p>
<p><em>Bombus impatiens</em>; photo by USDA, Flickr</p>
<p><em>Bombus impatiens</em>; photo by USDA, Flickr</p>
<p><em>Bombus impatiens</em>; photo by USDA, Flickr</p>
<p><em>Bombus impatiens</em>; photo by USDA, Flickr</p>
<p><em>Bombus fervidus</em>; photo by Alan Schmierer, Flickr</p>
<p><em>Bombus fervidus</em>, dorsal view; photo by Hanna Royals, USDA APHIS PPQ ITP</p>
<p><em>Bombus fervidus</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Bombus huntii</em>, dorsal view; photo by Hanna Royals, USDA APHIS PPQ ITP</p>
<p><em>Bombus huntii</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Bombus pennsylvanicus</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Bombus occidentalis</em>, lateral view; photo by Todd Gilligan, USDA APHIS PPQ ITP</p>
<p><em>Bombus fervidus</em> (left) compared to <em>Vespa mandarinia</em> (right), dorsal view; photos by Hanna Royals and Todd Gilligan, USDA APHIS PPQ ITP</p>