Loading profile. Please wait . . .
Bombus affinis Cresson, 1863
Rusty-patched bumblebee
Federal Protection: Listed Endangered
State Protection: Endangered
Global Rank: G2
State Rank: SH
Element Locations Tracked in Biotics: Yes
SWAP 2015 Species of Greatest Conservation Need (SGCN): Yes
SWAP 2025 Species of Greatest Conservation Need (SGCN): Yes
2025 SGCN Priority Tier: Data Deficient
Element Occurrences (EOs) in Georgia: 19
Habitat Summary for element in Georgia: historically found in northern mountains
The rusty patched bumblebee is a large species, with queens averaging anywhere from 19-23 mm (0.75-0.92 inch), while workers are 9-16 mm (0.37-0.64 inch) and males are 14-17 mm (0.55-0.66 inch). All males and most workers possess a small rusty patch on either one or two of their abdominal segments. The thorax and first two abdominal segments are covered in a dense, yellow pubescence, while all other abdominal segments possess black pubescence. The head and legs of all specimens are black.
This species may be visually similar to the brown-belted bumblebee, B. griseocollis, and the red-belted bumblebee, B. rufocinctus. Moderately long pubescence distinguishes the rusty patched bumblebee from both species. A black stripe running down the center of the thorax, between the wings, easily discerns it from B. griseocollis. Black hair on the upper portions of the face and head further distinguishes it from B. rufocinctus.
The rusty-patch bumblebee can be found in a variety of habitats, including savannas, prairies, wetlands, urban parks, and gardens. This species is still commonly observed in the gardens of several major cities. The fact that this species is most often found in urban gardens today suggests that it is not tied to a specific habitat type, but rather that it requires diverse floral communities and an appropriate climate. Nests are underground or at ground level, often in abandoned rodent burrows, bunching grasses, rock piles, and similar situations.
The rusty-patched bumblebee forages on the flowers of a wide array of forbs, shrubs, and small trees. Recorded floral hosts include, but are not limited to: Agastache, Allium, Aralia, Aster, Dalea, Echinacea, Hydrangea, Liatris, Malus, Monarda, Robinia, Solidago, Symphyotrichum, and Vaccinium.
Like other Hymenoptera, the rusty patch bumblebee undergoes a complete metamorphosis.
Actively search among patches of preferred floral hosts. Bee bowls and Malaise traps may also be fruitful.
The rusty patch bumblebee is found within the eastern Interior Plains region, down through the Appalachian Highlands, and stops before reaching the Coastal Plain. Today, it is still present and commonly observed in urban areas just beneath the Great Lakes.
There are several threats which have led to the rusty patch bumblebee being recognized as the first federally-listed, endangered bee. Loss of diverse, florally-rich, open habitat like savannas and prairies has reduced suitable habitat where the species may forage, overwinter, and nest. Another significant factor in their decline is the transmission of pathogens from managed greenhouse bumblebee colonies. Other threats include climate change, irresponsible insecticide use, and competition from exotic invasive bees.
| Threat 1 | Threat 2 | Threat 3 | |
|---|---|---|---|
| General Threat | Climate change & severe weather | Invasive & other problematic species, genes & diseases | Natural system modifications |
| Specific Threat | Habitat shifting & alteration | Problematic species/diseases of unknown origin | Fire & fire suppression |
This bee is generally accepted to be extirpated in Georgia, although more surveys should be conducted to confirm.
Offer food and shelter for rusty-patched bumblebees by retaining or planting native grasses, as well as a variety of nectar and pollen-producing plants. Growing a diverse mix of blooming plants ensures that foraging opportunities will be present for bees throughout the seasons. Hedgerows and native woodlots can provide safe nesting sites. Avoid the use of chemical pesticides, especially in areas where rusty-patched bumblebees are known to occur.
Mitchell, Theodore B. Bees of the Eastern United States. Vol. 2. North Carolina Agricultural Experiment Station, 1960.
Brady S. Dunaway
12/2/2019
