At 10:07 AM 4/5/02 +0100, you wrote:
>I am not particularly surprised that they could do this , but I would like
>to understand the mechanism whereby they 'know' where a blocked up hole is
>so that they can unblock it.


I'm using a combination innercover, insulated and ventallation top box this
past winter.  It includes an upper entrance similar to the Bee Culture article
last year on overwintering single deeps.  I was a bit concerned when the
bees nearly sealed the openings with propolis.  But now that we have some
warmer weather they have mostly opened them again.  Seems if you  give
them something they can manage (not too big an opening) they do pretty
well on their own.  Time will tell, this past winter wasn't a good test case.

-Tim