Most bees and wasps hibernate during the colder months. In many species, only the queen survives the winter, emerging in spring to reestablish a colony. But honey bees remain active all winter long, despite the freezing temperatures and lack of flowers on which to forage.
The honey bee colony's ability to survive the winter depends on their food stores. Keeping warm takes energy in the form of honey. If the colony runs short of honey, it will freeze to death before spring. The worker bees force the now useless drones from the hive, leaving them to starve. It's a harsh sentence, but one that's necessary for the colony's survival. Drones would eat too much of the precious honey, and put the hive in peril.
Once sources of forage disappear, the honey bees settle in for the winter. As temperatures fall below 57° F, the workers hunker down near their cache of honey. The queen stops laying eggs in late fall and early winter, since food stores are limited and the workers must focus on insulating the colony.
The honey bee workers form a cluster around the queen and brood, keeping them warm. They keep their heads pointed inward. Bees on the inside of the cluster can feed on the stored honey. The outer layer of workers insulates their sisters inside the sphere of honey bees. As ambient temperatures rise, the bees on the outside of the group separate a bit, to allow more air flow. As temperatures fall, the cluster tightens, and the outer workers pull together.
As it gets colder, the worker bees actively generate heat within the hive. First, they feed on honey for energy. Then, the honey bees shiver. They vibrate their flight muscles but keep their wings still, raising their body temperatures. With thousands of bees shivering constantly, the temperature at the center of the cluster will warm up considerably, to about 93° F! When the workers on the outer edge of the cluster get cold, they push to the center of the group, and other bees take a turn shielding the group from the winter weather.
During warmer spells, the entire sphere of bees will move within the hive, positioning themselves around fresh honey stores. During long spells of extreme cold, the bees may be unable to move within the hive. If they run out of honey within the cluster, the bees can starve to death just inches from additional honey reserves.