The Black and Gold Bumble Bee Rediscovered in Connecticut!

Tracy Zarrillo, Connecticut Agricultural Experiment Station, New Haven

Photo credit: Monica Nichols, Nichols Photography

You may not have heard of iNaturalist (https://www.inaturalist.org/), the crowd-sourcing citizen science biodiversity portal launched in 2008, but researchers interested in learning more about species distribution and status check this database regularly for new and important field observations. Just recently, three people in three different counties in Connecticut uploaded photos to iNaturalist of unusual bumble bees they had never seen before. Little did they realize that they were witnessing a species of bumble bee first-hand that had not been seen in Connecticut since 1919, Bombus auricomus, the Black and Gold Bumble Bee!

This species had been extremely rare in Connecticut, with only three historical female records (two from 1919 and one from 1905), but now with three photos on i-Naturalist in 2021. The 1905 specimen was netted from Lilac (Syringa sp.), but the 2021 observations were all visiting Beebalm (Monarda spp.). The most recent photos were from Milford, in a pollinator garden at the Connecticut Audubon Society Coastal Center at Milford Point; Portland, in a suburban flower garden largely composed of various Monarda spp. and Anise Hyssop (Agastache foeniculum); and Vernon, in a wildflower meadow at the Belding Wildlife Management Area.

This species is also rare throughout the Northeast and tends to be very localized. There are a few possible reasons for this species’ rarity. The first is that their colonies are very small, with only about 35 workers typically produced throughout the entire season (McFarland et al. 2015). The low numbers of individuals reduce the probability of detection. Another is that it may prefer large, open hayfields with minimal management (they nest on the surface of the ground). Although Connecticut is home to many farms and fields, farming practices may disrupt nest development, and abandoned fields from early in the 20th century have grown into forests. Another theory is that it is a “boom or bust” species, which is a natural pattern that happens in the insect world. Some years are good years for certain insects for unknown reasons, and their populations skyrocket.

The Black and Gold Bumble Bee prefers flowers such as Bee balm (Monarda), Nightshades (Solanum), Clover (Trifolium), St. John’s Wort (Hypericum), and Boneset (Eupatorium) (McFarland et al. 2015). Queens, workers, and males may be on the wing until October in Connecticut, so be on the lookout in your pollinator habitats! If seen, please take a photo and upload it to iNaturalist (please join the Pollinator Pathway iNaturalist project—go to projects and type in Pollinator Pathway) that way we can further document its presence in Connecticut. If this is a “boom year” let’s try to get as many records as possible! More eyes on the ground….or on the flowers!

Watch Tracy Zarrillo's interview on WSHU Public Radio - Rare Bumblebee Spotted In Connecticut For The First Time In 100 Years