>I've watched bees fly on 40 degree F. days and on a really bright sunny day,
>have seen them come out of the hive and within one second, dive into the
>snow. I've always suspected that they were confused by the sunlight bouncing
>off the snow, causing them to become disoriented.

This year I have an unusual wintering situation I have not had for many
years now.  Many of my stands are within igloos.  The stands (lines of five
hives) are drifted right over with snow.  Some have a single chimney (a pipe
straight up through the snow usually over the top entrance of the strongest
hive).  But when I open the igloo there is a good size cavity at the front
of the hives and all the top entrances are connected to it.  There is only
one pipe because it vents the air from the whole stand.  A few igloos have
no pipe but the hives have been alive.  The top 20 to 30 cm. of snow is not
too icy yet, and the hives seem to be getting enough gas exchange through
the snow (but I have been shoveling these out a bit, as I would not want
them to get ice on top of the snow).

There is very little sunlight penetrating the snow drifts.  I have noticed
feces all over the insides walls of the igloo and the outside of the hives
where the bees have been going out, but walking, not flying.  I do not think
that they are freezing as is usual, because I did not see many dead bees on
the inside wall of the igloos I opened.  However, I may not be seeing
collections of them down at the bottom of the igloo, because the space gets
narrower lower down on the hives and I wasn't looking down there.

Regards,
Stan