> A couple of years ago, I set a smaller hive on top of a larger hive
> separated by a 3/8 inch sheet of plywood.  One of those combination
> indoor/outdoor thermometers was hung on the outside of
> the hive with its probe laid on top of the plywood sheet. The
> temperature from the inside probe read just about the same as the
> outside air temperature.

That's right, and putting one hive on top of another makes checking the
bottom hive difficult, plus it means that the bottom hive gets no top
insulation, and if any part of winter wrap matters, top insulation is it.

Moreover, bees will tend to drift up to the top hive in spring, sometimes
depleting it somewhat.

In  my opinion any real boost the top hive gets is from being up, off the
cold ground -- especially if the hives are in a dip or on a flat spot where
a hive is close to the ground, like a single, will suffer compared to hives
where the cluster is higher up, like doubles and triples.  The same effect
can be had by rigging a high stand, or, as we did, placing the single on a
dummy hive.

allen
A Beekeeper's Diary: http://www.honeybeeworld.com/diary/

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