Rusty-patched Bumble Bee

Bombus affinis

Classification

Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Hymenoptera
Family: Apidae
Subfamily: Apinae
Tribe: Bombini
Genus: Bombus
Species: affinis

Pronunciation

How to pronounce Bombus affinis: /ˈbɒmbəs əˈfɪnɪs/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Images

Bombus (Bombus) affinis by the Smithsonian. Used under a CC0 license.

Summary

Bombus affinis, the rusty patched bumble bee, is an endangered species that has experienced drastic population declines across its historical range in North America. It plays a crucial ecological role as a pollinator of various plants and has significant implications for agriculture.

Physical Characteristics

Queens are about 20–22 mm in length and 9–11 mm in width; workers typically about 10–16 mm in length and 6–9 mm in width; males are 13–17.5 mm in length. All members have a black hair-covered head with yellow and rust-colored patches on the abdomen. Males sometimes have pale hair present.

Identification Tips

Queens and workers have different color patterns, with workers showing a distinctive rusty-orange patch across the base of T2, and a well-defined black interalar band. The facial morphology differs greatly between affinis and similar species, with affinis having a shorter malar space and black facial hairs.

Habitat

Nests are typically built underground in locations like old rodent burrows, fields, wetlands, and occasionally above ground in grass and soil clumps. Foraging occurs in sand dunes, farmland, and wooded areas, necessitating long flowering seasons from April to October.

Distribution

Historically throughout eastern and upper Midwest United States, north to Ontario, Canada, east to Quebec, south to North Carolina, and west to the Dakotas. Significant declines in population noted across its range, particularly in the Midwest and New England.

Diet

Nectar and pollen from flowers of various plant species such as Abelia grandiflora, Asclepias syriaca, Lobelia siphilitica, Linaria vulgaris, and Antirrhinum majus, with a special reliance on certain plants for pollination such as Dutchman's breeches (Dicentra cucullaria).

Life Cycle

Colony initiation begins in spring with solitary queens emerging first and foraging for food. Eggs hatch roughly four days after fertilization, workers begin to gather food around mid-summer, and colonies can last about 4-5 months, with new queens emerging towards season's end.

Reproduction

Queens mate in summer and enter diapause for winter. Worker reproduction is suppressed by the queen's presence, leading to a social structure where dominant queens are crucial for colony success. Oophagy and larval ejection may occur in response to brood parasitism by Bombus bohemicus.

Predators

Predators of B. affinis include various birds and other insects; its colonies can also be compromised by parasitism from Bombus bohemicus.

Conservation Status

Endangered under the Endangered Species Act (ESA); Critically Endangered in the IUCN Red List.

Ecosystem Role

Vital pollinator for numerous plant species, including those important for agriculture. Essential for maintaining biodiversity and ecosystem health.

Economic Impact

Pollinate key agricultural crops including cranberries, plums, apples, onions, and alfalfa, playing a crucial role in food supply and ecosystem stability.

Cultural Significance

Plants pollinated by B. affinis, such as Aralia and Spiraea, hold medicinal importance to the First Nations peoples of Canada, indicating cultural ties to the bumblebee species.

Health Concerns

Susceptible to Apicystis bombi, a pathogen that can decrease worker populations and reproductive success, as well as threaten colony establishment.

Evolution

B. affinis is closely related to Bombus franklini within the subfamily Apinae. It exhibits distinctively different coloration patterns between sexes, unlike many other bumblebee species.

Similar Taxa

Misconceptions

Often confused with other bumblebee species due to similar morphological traits, particularly in coloration and body size.