rupestris is one of the Cuckoo Bees, so called
because of their habit of finding a nest of their host
species and infiltrating it. Cuckoo Bees have no worker
caste, only males (Drones) in late Summer/Autumn and
females (Queens) Only the young Bombus rupestris
Queens over-winter and emerge later than their hosts the
following Spring, to take over a nest of Bombus
lapidarius. The existing Bombus lapidarius Queen
is usually killed and the Bombus rupestris Queen
takes over the colony and produces her own eggs, which
the Bombus lapidarius workers tend, till new
males and females emerge during the Summer months.
Photographed at Sherwood Forest CP in May 2010.