Bombus citrinus

(Smith, 1854)

lemon cuckoo bumblebee

Bombus citrinus is a cuckoo bumblebee native to eastern North America, recognized by its lemon-yellow coloration. As an obligate social , it invades colonies of other bumblebees, kills the resident , and assumes control of the . It belongs to the subgenus Psithyrus, a group of parasitic bumblebees that have lost the ability to collect pollen and rear their own workers.

Bombus (Psithyrus) citrinus by the Smithsonian. Used under a CC0 license.

Pronunciation

How to pronounce Bombus citrinus: //ˈbɒmbʊs sɪˈtraɪnəs//

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Lemon-yellow extending to abdominal segments T4 or T5; with black hair intermixed with some yellow hairs; no black band between wing bases on thorax. Hind leg outer tibial surface convex and densely hairy, lacking pollen-carrying corbiculae. Wings slightly opaque, reddish brown to brownish black. Metastomal hairs short and even, longer on T5; T6 matte with dense punctures. Male genitalia diagnostic: gonostylus lined with long hairs, yellow volsella with much shorter hairs, valve long and thin and relatively straight compared to other Bombus .

Images

Distribution

Eastern North America: eastern to central Canada, northeastern United States, and parts of midwestern and southeastern United States.

Diet

Pre-invasion foraging observed on asters, thistles, snakeroots, blazing-stars, mountain-mints, and goldenrods.

Host Associations

Bombus impatiens - primary common eastern bumblebee
Bombus vagans - primary half-black bumblebee

Behavior

Invading locates nest by trailing chemical signatures left by host . Revisits nest to assess suitability before infiltration. May be attacked at nest entrance by host workers or may evade detection by chemical camouflage. Upon entry, kills host queen, , and larvae. Establishes dominance through aggressive mauling : rubbing body against host workers, grabbing and lateral sides with and forelegs, and making stinging motions. Mauling transfers chemical signatures and suppresses host worker ovarian development. Host workers subsequently rear offspring.

Ecological Role

Obligate social ; impacts of bumblebee .

Similar Taxa

Bombus insularisClosely related member of subgenus Psithyrus; both are cuckoo bumblebees with similar parasitic
Bombus variabilisClosely related member of subgenus Psithyrus; historically subgrouped with B. citrinus as Citrinopsithyrus or Laboriopsithyrus