Psithyrus(redirected from Cuckoo bumblebee)
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a genus of bees that are closely related to bumblebees (family Bombidae) and that parasitize their nests. Psithyri females deposit their eggs in the nests of the bumblebee hosts, which rear the young of the parasitic bees as their own. Adult psithyri are also accepted by the bumblebees as their own and are not driven from the nests. Psithyri greatly resemble their hosts in appearance; the female psithyri can only be distinguished from female bumblebees by the absence of pollen combs and pollen baskets on their legs.