New York Natural Heritage Program
Rusty-patched Bumble Bee
Bombus (Bombus) affinis Cresson, 1863
Insects

Identifying Characteristics [-]
Rusty-patched bumble bee workers and males have yellow hair on most of the thorax and abdominal segments one and two with a rusty brown patch on the front half of the second abdominal segment. The hairs on the head and other abdominal segments are black. There is a patch of black hair in the middle of the thorax extending into a "V" shape toward the rear (Evans et al.2008, Evans 2009). Queens are larger with the same coloration except they do not possess the rusty patch. Queens are generally 21-22 mm long, 9.5-11 mm wide. Workers are 11-16 mm long and 5-9 mm wide and males range from 13-17.5 mm long and 5-7 mm wide (Evans et al. 2008).
Rusty-patched Bumble Bee Images
click to enlarge
The Best Time to See
Bumble bee queens hibernate over the winter, emerge in the spring, locate a nest site, and rear young (workers, males, and new queens). After new queens and males mate, all males, workers, and old queens die by the beginning of winter and new queens settle into sites to overwinter (Schweitzer et al. 2012). The best time to see queens would be early spring. Adults may be observed throughout the active months of April into November.
J F M A M J J A S O N D
Present Active Reproducing
The time of year you would expect to find Rusty-patched Bumble Bee present (blue shading), active (green shading) and reproducing (orange shading) in New York.
Similar Species
  • Half-black bumble bee (Bombus (Pyrobombus) vagans)
    Half-backed bumble bee females have yellow hair on most of the first two abdominal segments and yellow on the top of their heads, but rusty-patched bumble bees have a rusty patch on the second segment and black on the top of their heads (Evans et al. 2009).
  • Lemon Cuckoo bumble bee (Bombus (Psithyrus) citrinus)
    Lemon cuckoo bumble bee males have yellow hair on most of the first two abdominal segments and yellow on the top of their heads, but rusty-patched bumble bees have a rusty patch on the second segment and black on the top of their heads (Evans et al. 2009).