Wikipedia
Bombini
The Bombini are a tribe of large bristly apid bees which feed on pollen or nectar. Many species are social, forming nests of up to a few hundred individuals; other species, formerly classified as Psithyrus cuckoo bees, are brood parasites of nest-making species. The tribe contains a single living genus, Bombus, the bumblebees, and some extinct genera such as Calyptapis and Oligobombus.