Lemon Cuckoo Bumble Bee

Bombus citrinus

Classification

Phylum: Arthropoda
Subphylum: Hexapoda
Class: Insecta
Order: Hymenoptera
Family: Apidae
Subfamily: Apinae
Tribe: Bombini
Genus: Bombus
Species: citrinus

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.

Images

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

Summary

Bombus citrinus, or lemon cuckoo bumblebee, is a specialist social parasite that invades the colonies of other bumblebees, particularly those of B. impatiens and B. vagans. It is characterized by its striking lemon-yellow coloration and unique life cycle that involves usurping the host's colony to reproduce.

Physical Characteristics

The thorax is predominantly yellow, and the outer tibial surface of the hind leg is convex and densely hairy. The head is teardrop-shaped with black hair and some yellow hairs. The male genitalia features long hairs on the gonostylus, while the penis valve is long, thin, and relatively straight compared to other bumble bees. The wings vary from reddish brown to brownish black and yellowish during pubescence, sometimes interspersed with black hairs.

Identification Tips

Look for the predominantly yellow thorax and the specializations of the hind leg tibiae. The lack of black hairs on the thorax and the specific features of male genitalia can help distinguish this species.

Habitat

Found in various habitats throughout eastern to central North America, particularly where host bumblebee species are present.

Distribution

Located in eastern to central parts of Canada, northeastern U.S. states, and parts of the midwestern and southeastern regions of the U.S.

Diet

Both sexes feed on nectar from various flowers including asters, thistles, snakeroots, blazing-stars, mountain-mints, and goldenrods.

Life Cycle

Bombus citrinus is an obligate social parasite that invades other bumblebee colonies, primarily B. impatiens and B. vagans, where it kills the resident queen and lays eggs that are cared for by the host workers.

Reproduction

Females locate a host nest, infiltrate it, kill the host queen, and then lay their eggs, which are cared for by the host species' workers.

Ecosystem Role

As a social parasite, B. citrinus interacts closely with its host species, influencing their populations and dynamics.

Evolution

Belongs to the subgenus Psithyrus, previously classified as its own genus with a divergence around 20 million years ago from related Bumblebee subgenera. Coevolved with host species around 2 million years ago.

Similar Taxa

Misconceptions

Commonly mistaken for other species; however, its cuckoo parasitic behavior distinguishes it from typical bumblebees.