Bees employ various strategies to survive winter, with survival mechanisms depending on the species and their social structure. Some bee colonies remain active, while others rely on a single individual or developing young to persist until warmer weather returns.
Honey Bees: Huddling for Warmth
Honey bee colonies remain active through the winter. As temperatures drop below approximately 57°F (14°C), worker bees form a compact “winter cluster” inside their hive to generate and conserve heat. This dynamic sphere of bees has individuals constantly moving between the warmer core and cooler outer layers. The outermost bees form a dense, insulating mantle, periodically rotating into the warmer center.
Inside the cluster, bees generate heat by rapidly vibrating their flight muscles without moving their wings. This consumes energy, supplied by their stored honey. The colony maintains a core temperature of around 93-97°F (34-36°C) when brood is present, or slightly lower, around 85°F (29°C), if no brood is being reared. The queen bee is typically located within the warm center, and worker bees prioritize keeping her warm.
The cluster’s size and density adjust with external temperatures, contracting when colder to reduce heat loss and expanding on warmer days. Throughout winter, the cluster shifts within the hive to access stored honey. Honey bees must collect substantial honey during warmer months to fuel heat production and sustain the colony. If the honey supply is exhausted or the cluster becomes too small to maintain adequate warmth, the colony can perish.
Other Bees: Diverse Winter Fates
Unlike honey bees, bumble bees do not maintain an active colony through the winter. The entire colony, including the old queen, worker bees, and male drones, dies off as autumn progresses. Only newly mated queen bumble bees survive the cold months.
These new queens find sheltered locations, such as burrows, under leaf litter, or in rotten logs, where they enter a state of hibernation. They rely on fat reserves accumulated in the fall. Some queens produce a natural antifreeze, glycerol, to prevent ice crystals from forming in their cells. In spring, these queens emerge to establish new nests and begin new colonies.
Solitary bees, which make up the vast majority of bee species, have varied winter survival methods. Unlike social bees, solitary bees do not live in colonies. Most adult solitary bees live for only a few weeks during warmer seasons and die before winter. Their survival depends on their offspring, which typically overwinter as larvae or pupae within individual nest cells.
These developing bees are sealed inside protected structures, such as hollow plant stems, tunnels in wood, or chambers excavated in the soil. Mason bees, for example, overwinter as adults inside cocoons, while leafcutter bees overwinter as a pre-pupal stage. They remain dormant throughout winter, consuming food provisions left by their mother. As temperatures rise in spring, they complete development into adult bees and emerge.