Other Common Names
Often cited as Twospotted Bumble Bee, but use of a hyphen is generally preferred when citing common names (see AOU and BOU bird checklists, e.g., Three-toed Woodpecker).
Synonyms and other taxonomic changes
Formerly Bombus ridingsii
Explanation of Names
Bombus bimaculatus Cresson 1863
The specific epithet and common name refers to the two distinctive yellow markings on the abdomen.
Size
Queen: body length 17-22 mm. Worker: 11-16 mm. Male: 13-14.5 mm. Relatively small.
Identification
see detailed description of queen and male at
discoverlife.org; worker is very similar to queen but smaller.
In female the yellow of second abdominal tergum (T2) extends in a deep "U" nearly to the apex of the segment medially but the lateral portions of T2 are very largely red. Thus the yellow is very extensive medially but not laterally. In griseocollis the yellowish-brown of T2 forms a shallow "U" which does not extend far posteriorly in the middle but is relatively more extensive laterally thus appearing more as a transverse band than as a medial strip of yellow.
The female vertex is extensively yellow, more so than in impatiens, and unlike griseocollis which has entirely black vertex hairs. The female scutum has a conspicuous circular black spot.
The malar space of both sexes is notably long as in vagans, much longer than in impatiens, and very much longer than in griseocollis. Structure is useful to check as the yellow T2 hairs of female bimaculatus can be inconpicuous, and impatiens can have some yellow hairs on T2 basally.
The hue of yellow is more lemony than in impatiens or griseocollis.
Males are highly variable. Most can be recognized by their long face in combination with black corners of T2 but in many this is reduced to mere spots and in some to a few black hairs only so that T2 appears mostly yellow. In the more yellow males a yellow T1-T2 is followed by a narrow, contrasting black hair band on T3.
Range
Eastern North America: Ontario to Maine, south to Florida, west to Mississippi
Season
March to September; as early as February in Florida
Food
This species has a long tongue for its subgenus so can extract nectar from long floral tubes such as those of mints (Lamiaceae). The Hosts section on its
Discover Life species page lists known floral associations based on specimen records and images.
See Also
B. griseocollis, distinguished by the hair on the head that is all black.
Print References
Mitchell, T.B. 1962 Bees of the Eastern United States. North Carolina Agricultural Experiment Station Technical Bulletin No. 152.
LaBerge, W.E., and Webb, M.C. 1962. The Bumblebees of Nebraska. University of Nebraska College of Agriculture-Agricultural Experiment Station, Research Bulletin No. 205.
Internet References
status in Iowa and extensive info on bumble bees in general (holoweb.com, Minnesota)
common name reference; PDF doc (Committee on Common Names of Insects, Entomological Society of America)
