As temperatures drop and days shorten, the vibrant activity of summer’s buzzing bees often fades. Bees do not simply disappear; they employ diverse survival strategies to endure winter. While some insects truly hibernate, bees exhibit varied behaviors, from communal warmth to solitary dormancy, each tuned to their species and environment.
Honey Bee Winter Behavior
Honey bee colonies, unlike many other bee species, survive winter as a collective unit. When outside temperatures fall to about 57°F (14°C), worker bees form a dense, spherical cluster inside their hive, known as a winter cluster. This cluster generates and conserves heat for the colony. The bees on the outer layer pack tightly, acting as insulation, while bees in the core remain looser and generate heat by vibrating their flight muscles. This muscle vibration, similar to shivering, burns calories and produces warmth.
The queen bee is kept at the core of this cluster, where the temperature is maintained between approximately 80°F to 93°F (29°C to 34°C). If the colony needs to raise brood during late winter or early spring, the core temperature can be elevated to a consistent 91-98°F (33-37°C) to support the developing young. The cluster slowly moves across the honeycomb throughout winter, consuming the honey stores they collected. These food reserves provide energy for heat generation and sustenance until spring.
During the coldest periods, honey bees minimize activity, reducing or stopping brood rearing entirely. Drones, the male bees, are typically expelled from the hive in the fall, as they do not contribute to winter survival. The worker bees that emerge in the fall are physiologically different from their summer counterparts; they live for several months, whereas summer workers typically live only about six weeks. This extended lifespan allows them to bridge the gap between generations, ensuring the queen and a core group of workers survive to restart colony growth in spring.
Bumble Bee Winter Behavior
Bumble bees employ a different winter survival strategy. Entire bumble bee colonies do not typically survive winter; instead, only new, fertilized queens endure the cold months. As autumn approaches, the existing colony, including the old queen, workers, and males, naturally declines and dies off.
The newly mated queens feed extensively to build up fat reserves for their solitary hibernation. These overwintering queens seek sheltered locations, often burrowing into soft earth, under logs, or beneath stones. They enter a hibernation-like state where their metabolism slows significantly. Some species may even produce glycerol, a natural antifreeze, to protect their cells from freezing.
The queen remains in this dormant state until spring arrives, when rising temperatures and blooming flowers signal it is time to emerge. Upon emergence, she will forage to regain strength and then search for a suitable site to begin a new colony.
Solitary Bee Winter Behavior
Solitary bees, comprising the majority of bee species, exhibit diverse winter survival methods, but none involve forming communal colonies. Adult solitary bees generally do not survive winter; instead, the next generation overwinters in various developmental stages. These bees often spend the cold months within individual nests constructed by their mothers.
Many solitary bee species, such as mining bees, nest underground, creating individual cells for their offspring. Others, known as cavity-nesting bees, utilize hollow plant stems, tunnels in wood, or pre-existing burrows. Inside these protected nests, young bees typically overwinter as larvae or pupae. For instance, some species may overwinter as non-feeding larvae (prepupae) inside cocoons, while others develop into pre-emergent adults that remain dormant within their cells.
These developing bees enter a state of torpor or diapause, conserving energy and halting their development until environmental conditions become favorable. The nest structure itself provides insulation, protecting vulnerable young from extreme cold and dampness. When spring arrives, these dormant larvae or pupae complete their metamorphosis into adult bees and emerge from their nests, ready to begin the cycle anew.