Rusty-patched bumble bee

Conservation Status

IUCN Red List

CR - Critically Endangered

NatureServe

NNR - Unranked
SNR - Unranked

Federal

Endangered

Minnesota

not listed

Species in Greatest Conservation Need

Description

Rusty-patched bumble bee is a relatively large colonial bumble bee. It was historically common throughout most of its range, which extended from Maine to Georgia, west to Minnesota, with a few individuals found in North Dakota. Since the 1990s populations have declined severely in 87% of its historical range. It currently occurs in Minnesota, Iowa, Wisconsin, Illinois, and Indiana, and there are a few widely scattered recent records from Ontario, Quebec, Ohio, New York, Massachusetts, Virginia, and West Virginia.

The female (worker) bee is 7⁄16″ to ⅝″ (11 to 16 mm) long. The width of the abdomen is 3⁄16″ to 5⁄16″ (5 to 8 mm).

The hairs on the head are entirely black, including a dense band of hairs on top of the head (vertex) at the rear. The antennae have 12 segments consisting of one basal segment (scape), one small connecting segment (pedicel), and ten more segments (flagellomeres). The scape is long, slightly more than half as long as all of the flagellomeres together. The first flagellomere is slightly longer than the third, and the third is somewhat longer than the second. The tongue is short, shorter than any other bumble bee species.

The upper side of the thorax is densely covered with long, mostly yellow hairs. The hairs near the flap-like covering of the wing bases (tegulae) are black intermixed with yellow. Between the wings there is a band of black hairs that extends toward the rear in a V shape.

The abdomen has six segments and is densely covered with relatively long hairs. The hair on the first segment is entirely yellow. On the second segment it is mostly yellow except for a rusty-red patch in the middle. On the remaining segments the hairs are entirely black.

The wings are clear and lightly tinted brown.

The legs are black and are covered with mostly black hairs.

The queen is similar but larger, 13⁄16″ to ⅞″ (21 to 22 mm) in length. The pubescence is shorter and less dense. The thorax has a round, bare, black spot in the middle surrounded with intermixed black and yellow hairs. The second abdominal segment is entirely yellow, with no rusty patch.

The male (drone) is somewhat larger, ½″ to 11⁄16″ (13.0 to 17.5 mm) in length. It is similar to the worker, but the abdomen has 7 segments, and the antennae have 13 segments. The band of hairs on the vertex has a few pale hairs intermixed. The hairs on abdominal segments 1 and 2 are entirely yellow.

Size

Male: ½″ to 11⁄16″ (13.0 to 17.5 mm)

Worker: 7⁄16″ to ⅝″ (11 to 16 mm)

Queen: 13⁄16″ to ⅞″ (21 to 22 mm)

Similar Species

Habitat

Ecology

Season

Mid-May through late October

Behavior

Life Cycle

Rusty-patched bumble bee usually nests in the ground in an abandoned rodent burrow.

Larva Food/Hosts

Adult Food

Distribution

Sources

6, 24, 27, 30, 82, 83.

Biodiversity occurrence data published by: Minnesota Biodiversity Atlas (accessed through the Minnesota Biodiversity Atlas Portal, bellatlas.umn.edu. Accessed 7/9/2026).

Bombus affinis Cresson, 1863 in Bánki, O., Roskov, Y., Döring, M., Ower, G., Hernández Robles, D. R., Plata Corredor, C. A., Stjernegaard Jeppesen, T., Örn, A., Pape, T., Hobern, D., Garnett, S., Little, H., DeWalt, R. E., Miller, J., Orrell, T., Aalbu, R., Abbott, J., Abreu, C., Acero P, A., et al. (2026). Catalogue of Life (2026-06-19 XR). Catalogue of Life Foundation, Amsterdam, Netherlands. https://doi.org/10.48580/dgy8b

Environmental Conservation Online System (ECOS), U.S. Fish and Wildlife Service, Rusty patched bumble bee (Bombus affinis), retrieved 7/9/2026.