Whether bees perish in winter depends entirely on the species. Bees have evolved various survival strategies to cope with cold temperatures and the lack of floral resources. These strategies vary drastically, ranging from collective social thermoregulation to a solitary, dormant state. The success of each method relies on complex physiological and behavioral adaptations.
How Honey Bee Colonies Survive Winter
The Western honey bee (Apis mellifera) is a social species that survives the winter as a complete colony, not as dormant individuals. When the ambient temperature drops below 50°F (10°C), worker bees form a “winter cluster,” a tight ball centered around the queen and stored honey reserves. Bees on the outer layer interlock their bodies to act as a living shell, while the bees inside generate heat.
Heat is produced through rapid, isometric contraction of their flight muscles—essentially shivering—which maintains the cluster’s core temperature between 68°F and 95°F (20°C and 35°C). Bees constantly rotate from the cold outer edge to the warmer core, ensuring no individual freezes and allowing the cluster to move across the honeycombs to access food. To support this sustained energy expenditure, the colony relies on the honey it stored during the warmer months, often consuming between 30 and 60 pounds of reserves in cold climates.
The worker bees that form this cluster are known as “winter bees” or “diutinus bees.” Unlike their summer counterparts, whose lifespan is only five to six weeks, these winter bees are physiologically distinct, accumulating larger fat body reserves and vitellogenin proteins. This enables them to live for four to six months, allowing them to bridge the resource gap until spring blooms. Before the cold sets in, male drones are expelled from the hive because they do not contribute to survival and consume limited food resources.
The Strategy of Solitary Bees
The vast majority of bee species are solitary, and their winter survival plan differs radically from the collective approach of honey bees. Solitary bees, such as mason bees or leafcutter bees, do not form colonies, and the adult female who built the nest often dies before winter. Survival rests on the next generation, which is sealed inside individual brood cells within tunnels or hollow stems.
These developing bees enter diapause, a genetically and hormonally regulated suspension of development and metabolic activity. Depending on the species, the bee may overwinter as an egg, a pre-pupa, or a fully formed adult encased in its cocoon. Each larva survives the long cold period by consuming the pollen and nectar provisions the mother bee packed into the cell before sealing it. The sealed nest and slowed metabolism protect the dormant insect until conditions are favorable for emergence.
What Happens to Bumble Bees
Bumble bees (Bombus species) employ a strategy intermediate between social and solitary bees. The entire colony, including workers, drones, and the old queen, is annual and dies with the onset of cold weather. Continuation relies solely on the new, mated queens produced late in the season.
These newly fertilized queens spend late fall gorging on nectar to build substantial fat reserves that sustain them for several months. The queen then finds a sheltered location, often underground in soft soil, leaf litter, or old rodent burrows, called a hibernaculum. She enters a deep state of torpor, a form of diapause where her metabolic rate is significantly reduced. This solitary hibernation allows the queen to survive the winter alone, ready to emerge in spring and found a new colony.
Signaling the Start of Spring
The end of the winter survival phase is triggered by environmental cues, primarily increasing ambient temperatures and the lengthening photoperiod (daylight hours). The rising warmth signals a return of floral resources, but the increase in daylight is the more reliable trigger for internal physiological shifts.
For the honey bee colony, these cues prompt the cluster to expand and the queen to resume significant egg-laying, raising new brood. The lengthening days signal the hibernating bumble bee queen to emerge from her subterranean shelter. Once awake, she begins foraging and searching for a suitable nesting site to lay the eggs that will become her first workers. Similarly, increasing temperatures and extended daylight trigger the final stages of metamorphosis and the adult solitary bee’s emergence.