An interesting two part paper entitled "Rethinking Our Ideas About the
Winter Cluster" appeared in the July 1998 edition of the American Bee
Journal.

Data was obtained from hives over wintered in various configurations such
as large cluster size, extra hive wall insulation, etc. Metabolic rates
were also obtained from caged bees at different ambient temperatures.

The importance of a "water balanced economy in an optimum size colony"
was proposed as a major factor controlling winter cluster behavior.

This idea explains much of the personal observations I have had
overwintering bees both indoors and outdoors in dry, cold climates such
as Wyoming and interior Alaska. It could explain some of the behaviours
attributed to temperature.

The bees efforts to limit upper ventilation may be an attempt to control
water resources rather than retain cluster heat . In climates that would
provide the winter cluster with sufficient water resources through
humidity, frost accumulations around the cluster or outside flight
activity, the impacts of upper ventilation and water balance may not be
so apparent.

The importance of water balance to the winter cluster was also
demonstrated by a Canadian beekeeper during the 1970's.  He used water
vapor to initiate brood rearing in indoor wintered colonies and sold the
extra early production as packages.  He wrote a series of articles for
the American Bee Journal. I have lost the references. Sorry!

During the spring the factors that provide an optimum hive environment
are drastically different that those during the winter. Wrapping,
ventilating or insulating a hive during one season could provide the
optimum environment for the bees. During a different season the same
treatment could kill or weaken the hive.

Best Wishes
Dennis Murrell