Bumble bees will dig into loose earth usually under leaf
litter ("the roof") in a well sheltered spot, under a tree or the face of a
steep hill. Occasionally, to aid herself in excavating a hibernaculum a bumble
bee gyne will rapidly vibrate the substrate with her thoracic flight
muscles to loosen soil. She literally
digs in for the winter. There is no true cavity, just the female
surrounded by an inch or so of loose soil. A gyne accumulates alot of
non-metabolizing fat reserves that will protect her vulnerable tissues from
extreme cold. Snow is also a wonderful insulation, especially in Canada
where it remains on the ground.
 
                                                Cheers,
                                                Blair
 
Blair Sampson
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