Whether bees survive the winter depends entirely on the species. Most bee species, including solitary bees and bumble bees, rely on individual survival; the adult colony dies, and the new generation or a single queen enters a state of deep dormancy. In contrast, the social honey bee colony operates as a unified, perennial organism that remains active all winter, collectively generating heat to survive as a group. This communal strategy requires large food reserves and physiological adaptation by the worker bees.
Honey Bee Survival: The Winter Cluster
Honey bee colonies survive cold temperatures by forming a dense winter cluster, which acts as a collective, warm-blooded organism. When the ambient temperature drops below approximately 57°F (14°C), the bees gather tightly on the honeycomb, creating an insulating formation that maintains internal warmth. The cluster is divided into two layers: a dense outer mantle and a looser inner core. Bees in the outer layer act as an insulating blanket, pressing their bodies close together to trap heat.
Heat generation occurs primarily in the core, where worker bees rapidly vibrate their thoracic flight muscles without moving their wings. This muscle flexing converts stored carbohydrate energy into metabolic heat. The bees slowly rotate from the colder outer mantle into the warmer core, ensuring the colony remains functional. If the colony is rearing brood, the core temperature is maintained at 81°F to 93°F (27°C to 34°C); otherwise, it is kept slightly cooler.
The colony’s survival depends on its stored fuel source: honey, which is consumed to power the heat-generating muscle contractions. As winter progresses, the cluster slowly moves across the combs, consuming the stored honey. If the cluster becomes too cold to move, or if the stored honey is physically separated from the cluster, the bees will starve. The queen remains at the center of the cluster, protected and warmed by the workers, and typically ceases egg-laying to conserve the colony’s resources.
How Solitary and Bumble Bees Overwinter
The survival strategy of most other bee species differs from the honey bee, as their colonies are annual and do not survive the winter. For bumble bees, the old queen, workers, and males perish with the onset of freezing temperatures. Only the newly mated queens, produced in late summer, survive by entering dormancy known as diapause. These new queens store large amounts of fat, then seek out a sheltered underground location, such as a cavity in the soil or under debris, where they remain motionless until spring.
Solitary bees rely on individual survival, though it is the next generation that endures the winter. The adult female solitary bees die after constructing their nests and provisioning them with food. The offspring spend the winter sealed within their individual cells, typically as dormant larvae or pupae.
Within their cocoons, these developing bees enter a state of torpor, drastically reducing their metabolism and energy consumption. They rely on the small ball of nectar and pollen provisioned by their mother, which sustains them through winter. They remain in this dormant stage, only completing their final metamorphosis and emerging as adult bees once spring arrives.
The Biological Shift: Preparing for Cold
The transition into winter survival mode is triggered by environmental signals, such as shortening daylight hours and falling temperatures. For honey bees, these late summer and early autumn signals prompt a physiological change in the worker population. The colony begins to rear a distinct generation known as “winter bees.”
These specialized winter bees possess enlarged fat bodies, storing energy. This physiological difference allows them to live for four to six months, compared to the four to six weeks of a summer worker. As resources dwindle, the colony ceases the production of male drones to conserve honey stores for the surviving female workers and the queen.
Bumble bees also undergo a shift. The colony stops producing workers and instead rears a final generation of males and new queens. These newly emerged queens spend the autumn foraging intensely to build up the fat reserves necessary to fuel their diapause before they emerge in the spring to start a new colony.