The question of what happens to bees when temperatures drop reveals distinct survival mechanisms across different species. While some insects, such as the Monarch butterfly, make long-distance journeys to warmer climates, the vast majority of bees found in temperate regions do not migrate. Instead of traveling, bees employ complex strategies to survive cold periods by remaining in or near their existing nesting sites. These methods range from collective heat generation within a colony to individual states of deep dormancy. Understanding these adaptations shows that bee survival is a localized effort focused on resource management and insulation.
Answering the Migration Question
The term “migration” involves a seasonal, two-way journey to a new habitat for feeding or breeding, which is not a behavior exhibited by common bee species. Bees adopt specialized overwintering strategies rather than relocating to a warmer geographical area, committing to surviving the cold season in place, either as a large group or as single individuals.
The survival strategy depends entirely on the bee’s social structure. Social bees, like the honey bee, manage cold temperatures collectively, while non-social species, such as solitary bees and bumble bees, rely on individual mechanisms. Widely known species in North America and Europe remain anchored to their homes, focusing on minimizing energy expenditure and sheltering from the cold until spring returns.
The Honey Bee Colony’s Winter Strategy
The European honey bee (Apis mellifera) survives the winter not by sleeping, but by forming a dense collective known as the winter cluster. This cluster begins to form when the outside temperature drops below approximately 57°F (14°C), marking the point when individual bees can no longer maintain their own body temperature. The entire colony functions as a single warm-blooded organism throughout the cold months.
The bees generate heat by vibrating their flight muscles without moving their wings, similar to shivering in mammals. The outer shell of the cluster is tightly packed, forming an insulating layer where temperatures hover between 46 and 57°F (8 and 14°C). The core of the cluster, where the queen resides, is actively heated.
If no new young are being raised, the core is maintained around 68°F (20°C); however, once egg-laying resumes in late winter, the core temperature is precisely regulated between 92 and 95°F (33 and 35°C). Bees constantly rotate between the cold outer layer and the warm inner core, ensuring no single bee freezes.
To fuel this continuous heat generation, the colony relies exclusively on the honey stored during warmer foraging months. A healthy colony may consume between 30 and 60 pounds of honey over the winter season. The cluster slowly moves across the honeycomb to access these stored food reserves, allowing the entire social unit to survive and quickly resume activity when spring arrives.
How Solitary Bees Overwinter
Solitary bees and bumble bees, which do not maintain perennial colonies, utilize a completely different, individual-based survival strategy. For most bumble bee species, the entire colony, including the workers and the old queen, dies off completely with the onset of cold weather. Only the newly mated queen survives to carry the lineage forward.
This new queen burrows into a small, sheltered cavity, often in loose soil, under leaf litter, or within a rotting log, a spot known as a hibernaculum. She enters a physiological state called diapause, which is a period of arrested development. During diapause, her metabolism slows dramatically and her body produces a cryoprotectant, such as glycerol, which acts as a biological antifreeze to prevent her internal tissues from freezing.
Solitary bees, like mason bees and leafcutter bees, also use diapause, but they overwinter in their natal nests. These bees typically pass the cold season as mature larvae, pupae, or pre-emerged adults sealed within individual cells they constructed in tunnels or hollow stems. The female bee provisions each cell with a pollen and nectar mixture before sealing it, providing the young with a food source for when they awaken in the spring.