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We were mooching around some limestone pavement yesterday and saw a
great many bumblebees (and other bees) coming out of holes in the
ground. Not nesting, though - they were diving down the grykes after the
various plants that were in flower, disappearing underground, with their
buzzing re-echoing around the hole they were in, then reappearing from a
completely different entrance.


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Is it possible that what you saw were mining bees? i was watching a load of these in my garden the other day. there are lots and lots of entrances. I am told they have a sting but it is very ineffectual.