A bumblebee, also written bumble bee, is a member of the bee genus Bombus, in the family Apidae. The brood parasitic or cuckoo bumblebees have sometimes been classified as a subgenus or genus, Psithyrus, but are now usually treated as members of Bombus. This genus is the only extant group in the tribe Bombini, though a few extinct related genera (e.g., Calyptapis) are known from fossils. Over 250 species are known, found primarily in higher latitudes or at higher altitude in the Northern Hemisphere, although they also occur in South America; however, a few lowland tropical species are known. European bumblebees have been introduced to New Zealand and Tasmania.