Explanation of Names
Bombus affinis Cresson, 1863
common name refers to the rust-colored patch on the abdomen.
queen: body length 21-22 mm
male: 13-17.5 mm
worker: 11-16 mm
Queens have a similar color pattern to B. vagans, with a yellow thorax and yellow T1 and T2 but in affinis the face and malar is much shorter, the hairs of the face are all black, and the coat is shorter and more uniform in length. Workers and males are distinctive in having a well-defined black interalar band (as opposed to a black medial spot) and in having an rusty-orange patch across the base of T2.
see detailed descriptions at discoverlife.org
MN to IN, plus a few remaining sites on east coast, see map per Xerces Society
. Formerly Upper Midwest and Eastern North America: Ontario to New Brunswick, south to North Carolina. Historically known from more than 25 states.
The Hosts section of its Discover Life species page
lists known associations based on specimen records and images.
Declines of this species were first noted by John S. Ascher at Ithaca, New York, ca. 2001 when populations that were conspicuous in the late 1990s could not be located. At this and many other localities across its historic range affinis is no longer detected, but it has been shown to persist locally in the midwest and in New England.
Abrupt and severe declines of this and other bumble bee species in this subgenus were widely reported soon after development of the commercial bumble bee industry and detection of high rates of parasitism in managed colonies.
U.S. Fish and Wildlife Service announced (Sept. 21, 2016) that it is proposing to list the rusty patched bumble bee as an endangered species under the Endangered Species Act. - Xerces Society
(fairly extensive amount of info)
33 pinned adult images
plus detailed descriptions of queen, worker, male, distribution, seasonality, flower records (discoverlife.org)
- Natural History Museum, UK
common name reference; PDF doc
(Committee on Common Names of Insects, Entomological Society of America)