Bombus (Thoracobombus) pensylvanicus (De Geer, 1773)

Zarrillo, Tracy A., Stoner, Kimberly A. & Ascher, John S., 2025, Biodiversity of Bees (Hymenoptera: Apoidea: Anthophila) in Connecticut (USA), Zootaxa 5586 (1), pp. 1-138 : 84

Bombus (Thoracobombus) pensylvanicus (De Geer, 1773)

American Bumble Bee

Notes: This well-known species was historically common throughout the eastern and central United States, and was at one time widespread throughout Connecticut, detected in pastures, fields, and meadows on flowers such as morning glory ( Ipomoea sp. ) and greater burdock ( Arctium lappa ). This species was also reported on black currant ( Ribes nigrum ), apple ( Malus domestica [as Pyrus malus ]), and common blackberry ( Rubus allegheniensis [as Rubus nigrobaccus ]) in Britton & Viereck (1906) [as B. pensylvanicus DeGeer and B. americanorum Fabricius] although vouchers were unable to be located. Bombus pensylvanicus has declined in the northern parts of its range in the United States (Williams et al. 2014), and it was last detected in Connecticut in 2006 at the Belding Wildlife Management Area in Vernon (Tolland County). The lack of records is notable given the extent of wild bee surveys in its preferred habitats, open farmland and fields (Williams et al. 2014), across the state since 2009. There is a petition to list B. pensylvanicus as an endangered species under the United States Endangered Species Act (Center for Biological Diversity & the Bombus Pollinators Association of Law Students 2021), and its status in Connecticut should be reviewed in upcoming endangered species assessments. Despite its genuine scarcity in Connecticut (found in 23 towns prior to the year 2000 and with only the one record noted above since) and in New England generally, this species, however, has the seventh most records globally (n = 41,208; sixth among Bombus species) of all wild (non- Apis ) bee species (n = 4,619) globally as reported on iNaturalist (accessed 16 September 2024) and has the fourth most records (n=40,451, most recent) of any wild bee species from North America and the United States raising doubts about whether it can be considered one of the most threatened taxa globally or nationally.