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Species Bombus flavidus - Flavid Cuckoo Bumble Bee

Bee from BugGuide Gathering - Bombus flavidus Bombus queen on Goldenrod - Bombus flavidus - female Bombus - Bombus flavidus Cuckoo Bumble Bee on Common Milkweed - Bombus flavidus High Elevation Bumblebee, North Carolina - Bombus flavidus Bombus - Bombus flavidus Bee-20190801 - Bombus flavidus Cuckoo bumble bee - Bombus flavidus
Classification
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon (Aculeata - Ants, Bees and Stinging Wasps)
No Taxon (Apoidea (clade Anthophila) - Bees)
Family Apidae (Cuckoo, Carpenter, Digger, Bumble, and Honey Bees)
Subfamily Apinae (Honey, Bumble, Longhorn, Orchid, and Digger Bees)
Tribe Bombini (Bumble Bees)
Genus Bombus (Bumble Bees)
No Taxon (Subgenus Psithyrus)
Species flavidus (Flavid Cuckoo Bumble Bee)
Other Common Names
Often cited as Fernalds Bumble Bee, but use of the possessive is generally preferred when citing common names (see AOU and BOU bird checklists, e.g., Franklin's Gull).
Synonyms and other taxonomic changes
Formerly in genus Psithyrus which is now considered a subgenus of Bombus.
Psithyrus tricolor
Psithyrus wheeleri
Explanation of Names
Author of species is Franklin, 1911.
Size
Relatively small. Female: 14.5-17 mm. Male: 13-15 mm (no workers).
Identification
Males often have a distinctive ring-like band of yellow on T4 more or less contrasting with the color of the other tergites (T1-T3 vary from mostly black to mostly yellow) and especially with T5 which is mostly black. Similar species have more pale hairs on T5 laterally so don't have such a well-defined subterminal ring. Both sexes often have a black face contrasting with extensive yellow hairs on the vertex. The distinctive projecting and shape of the female apical sternum is rarely visible in images. Males have rather long malar spaces.
Range
Widespread in Canada and the United States, from Alaska to California in the West, New Brunswick to North Carolina in the East.
Season
June to September.
Food
Social parasites of other bumble bees including. Both sexes regularly visit flowers for nectar. The Hosts section of its Discover Life species page lists known floral associations based on specimen records and images.
Life Cycle
Overwintered, mated females can be observed seeking the hives of their hosts in the spring. In late summer and fall males and young queens can be observed on flowers.
Remarks
Cuckoo bumble bees are social parasites within the hives of other Bombus species. They don't have workers and lack pollen and nectar collecting equipment.
Recent genetic work has suggested this species should be included under the Old World Bombus flavidus:
Lhomme, et al. Diversification Pattern of the Widespread Holarctic Cuckoo Bumble Bee, Bombus flavidus (Hymenoptera: Apidae): The East Side Story. Insect Systematics and Diversity, Volume 5, Issue 2, March 2021, 5, https://doi.org/10.1093/isd/ixab007.
Internet References
common name reference; PDF doc (Committee on Common Names of Insects, Entomological Society of America)