Breaking News from USDA (United States Department of Agriculture): No one has confirmed a sighting of Franklin's bumblebee since 2006—but the case isn't closed. Scientists just extracted DNA from museum specimens decades old, and the confession rewrites everything we thought about extinction.

www.secretpollinators.com

KEY SOURCES

Primary study

• Schweizer, R. M., Branstetter, M. G., et al. (2025). Museum genomics suggests long-term population decline in a putatively extinct bumble bee. PNAS, 122(43): e2509749122. DOI: 10.1073/pnas.2509749122. Published October 20, 2025. — whole-genome sequence data from 25 museum specimens spanning four decades; remarkably low heterozygosity; runs of homozygosity indicating historical inbreeding, with some individuals showing nearly entire chromosomes in ROH; effective population size declining from the late Pleistocene with further declines in the last 400 years, possibly linked to fire and drought.

Accompanying commentary

• The ghost of Bombus past: Investigating the mystery of an extinct bumblebee. PNAS (2025). DOI: 10.1073/pnas.2527315122 — reconstructed timeline of B. franklini effective population size against candidate stressors including glaciation, diploid male production, fire and drought, competition with managed honey bees, grazing, habitat loss, systemic pesticides, and pathogen spillover.

Institutional coverage

• UC Davis, "Population Decline of Franklin's Bumble Bee Wasn't Due to Pathogens, Museum Genomic Research Shows" (October 20, 2025) — most specimens came from the Bohart Museum of Entomology; genome reconstruction spans roughly 300,000 years of the bee's genetic history.
• USDA-ARS Tellus, Museum Artifacts that Tell More than History Lessons — Beenome100 project context; B. franklini as a generalist pollinator of primarily alpine flowering plants; last observed in 2006 and currently listed as endangered.
• Kathy Keatley Garvey, "Robbin Thorp and Franklin's Bumble Bee," UC ANR Bug Squad (October 2025) — Thorp monitored the species for 21 years until his death in 2019; sighting counts fell from 94 in 1998 to 20 in 1999, then single digits, with the last sighting in 2006.

Range and status

• U.S. Fish & Wildlife Service, Franklin's Bumble Bee Endangered Species listing (2021). fws.gov
• Thorp, R. W., Jepsen, S., Foltz Jordan, S., Evans, E., & Hatfield, R. (2010). Petition to list Franklin's bumble bee Bombus franklini as an endangered species. Xerces Society.
• Hatfield, R., Jepsen, S., Thorp, R., Richardson, L., & Colla, S. (2015). IUCN Red List assessment, Bombus franklini.

Related museum genomics on declining bumble bees

• Rohde, A., Branstetter, M. G., Mock, K. E., Knoblett, J., Pilliod, D., Everett, J., Galpern, P., & Strange, J. P. Population genetics of museum specimens indicate decreasing genetic resiliency: The case of two bumble bees of conservation concern. USGS.

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