Bombus pensylvanicus

(De Geer, 1773)

American bumblebee, Sonoran bumblebee

Bombus pensylvanicus is a threatened historically widespread across eastern North America. have declined approximately 90% since the early 2000s, with range contractions particularly severe in northern and eastern portions of its former distribution. The species is a long-tongued favoring open grassland and agricultural . It maintains a typical bumble bee colony cycle with queens initiating nests in early spring and colonies persisting until late autumn. The species is of significant conservation concern and has been proposed for Act protection.

Bombus pensylvanicus by (c) crseaquist, some rights reserved (CC BY), uploaded by crseaquist. Used under a CC-BY license.

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

Pronunciation

How to pronounce Bombus pensylvanicus: //ˈbɒmbəs ˌpɛn.sɪlˈvæn.ɪ.kəs//

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

Identification

Distinguished from B. sonorus by paler yellow coloration and different yellow-black banding pattern. Resembles B. fervidus and B. auricomus, leading to frequent confusion; careful examination of pronotal hair color and scutellum pattern required. Sometimes mistaken for B. terricola or B. auricomus. Closest relative is B. sonorus, though the two maintain differences in male genitalia and do not hybridize broadly despite geographic overlap.

Images

Habitat

Open farmland, fields, and grasslands. Nests constructed in bundles of hay or long grass above ground, or in established crevices and burrows including old bird nests, rodent burrows, and cinder blocks. Occasionally nests in human-made objects such as buckets and barns.

Distribution

Eastern Canada, eastern and central United States, and Mexico. Historical range extended from Eastern Great Plains to Atlantic coast; now significantly contracted in northern and eastern portions. Extirpated from some areas; critically low in Pennsylvania and other former strongholds.

Seasonality

Colonies active February through November or December. Queens emerge from hibernation in March to establish nests. Reproductive phase begins July–August. Males become increasingly common in late summer. Activity pattern in subtropical zones resembles that of temperate-zone , with periods of inactivity.

Diet

Feeds on nectar and pollen; documented preference for sunflowers (Helianthus) and clovers (Trifolium). Foragers with shorter observed in mixed- flower stands, suggesting resource partitioning based on corolla length.

Life Cycle

Haplodiploid : unfertilized develop into males, fertilized eggs into female or queens. Colony cycle begins when mated queens enter hibernation until following spring. Queens establish colonies in March, provisioning wax pots with pollen and nectar. Egg-to- development takes 4–5 weeks. Colonies grow through summer, potentially exceeding 200 workers by late summer. production of inhibitory ceases when colony reaches sufficient size, triggering production of new queens and males. Workers may lay eggs but queens typically remove them; workers eventually sting queen to death in late summer. New queens mate and hibernate; colony dies off.

Behavior

Foraging range extends up to 1.5 miles from nest, with considerable individual variation in homing ability. Homing mechanism appears to involve trial-and-error rather than fixed instinct. Foragers exhibit mixed mating between flower types rather than strict flower constancy.

Ecological Role

Important native of agricultural crops and wildflowers. Contributes to pollination of sunflowers, clovers, and other plants. Serves as model for by robber fly Mallophora bomboides. to flies and cuckoo bee Bombus variabilis.

Human Relevance

Significant agricultural with historical abundance in southern United States. decline of nearly 90% documented since early 2000s prompted U.S. Fish and Wildlife Service status review for potential Act protection. Subject of conservation concern and research into causes of decline including loss, , , and climate change. First -level assembly published to support genetic research on decline mechanisms.

Similar Taxa

Bombus sonorusClosest relative; treated as by some authorities but maintained as distinct based on male genitalia differences and lack of hybridization across broad geographic overlap. B. sonorus shows darker yellow coloration.
Bombus fervidusResembles B. pensylvanicus in color pattern; requires careful examination of structural features for separation.
Bombus auricomusSimilar appearance leading to confusion; distinguished by specific hair patterns and coloration details.
Bombus terricolaOccasionally mistaken for B. pensylvanicus; differs in distribution and specific morphological traits.