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How do bees survive the winter?

Most bees hibernate. Only the queen survives the winter in many species, emerging in spring to reestablish the colony. It is the honey bees, the species Apis mellifera , that remain active throughout the winter, despite the low temperatures and the lack of flowers to feed on. And it is during the winter when they use what they have achieved with their hard work, feeding on the honey they have made and stored.

Apis mellifera. Apis mellifera.

The ability of honey bee colonies to survive the winter depends on their food reserves, consisting of honey, bee bread, and royal jelly. Honey is made from the collected nectar; bee bread is a combination of nectar and pollen that is stored in the cells of the comb, and royal jelly is a combination of honey and bee bread that nurse bees feed on.

Bee bread; the yellow cells of the honeycomb. Bee bread: the yellow cells of the honeycomb.

The energy that bees need to produce the heat that allows them to go through the winter is obtained from honey and bee bread; if the colony runs out of these foods it will freeze to death before spring arrives. In the evolution of the honey bee community, as winter approaches the worker bees drive the now useless drone bees out of the hive, leaving them to starve. This attitude, which may seem cruel, is essential for the survival of the colony: the drones would eat too much honey and endanger the survival of the colony.

When food sources disappear, the bees that remain in the hive prepare to spend the winter. When the temperature drops below 14 degrees, the bees are placed near their honey reservoir and honey bread. The queen bee stops laying eggs in late fall and early winter, when food becomes scarce, and the worker bees concentrate on isolating the colony. They huddle head-pointing into the hive, grouping around the queen and her young to keep them warm. The bees inside the cluster can feed on the stored honey. The outer layer of worker bees insulates their sisters and as the ambient temperature rises the bees on the outside of the group move apart a bit to allow air to flow through.

Arranged in this way, when the ambient temperature drops, the worker bees heat the interior of the hive. First they feed on honey for energy. The bees then contract and relax the muscles they use to fly, but keep their wings still, which raises their body temperature. With thousands of bees vibrating in this way, the temperature of the group rises to about 34 degrees. When the worker bees located on the outer edge of the group get cold, they push towards the center of the group and are replaced by other bees, thus protecting the colony from winter weather.

When the environment is warm, all the bees move inside the hive, reaching all the honey deposits. But during prolonged cold spells the bees may not be able to move within the hive; if the cluster they are in runs out of honey, they can starve even if they have food stores nearby.

A beekeeper at work. A beekeeper at work.

A colony of honey bees can produce about 12 kilograms of honey during a season, about two to three times what they need to survive the winter. If the colony is healthy and the season was good, they can produce about 30 kilograms of honey, much more than they need to survive.

Beekeepers can harvest surplus honey, but they must make sure to leave enough for the bees to survive through the winter.

Sources

Geraldine A.Wright, Susan W. Nicolson, Sharoni Shafir. Nutritional Physiology and Ecology of Honey Bees . Annual Review of Entomology 63 (1): 327–44, 2018.

Mark L. Winston. The Biology of the Honey Bee. Cambridge MA: Harvard University Press, 1991.

Robert Parker, Andony P. Melathopoulos, Rick White, Stephen F. Pernal, M. Marta Guarna, Leonard J. Foster. Ecological Adaptation of Diverse Honey Bee (Apis mellifera) Populations . PLoS ONE 5 (6), 2010. d oi.org/10.1371/journal.pone.0011096