Bumble bees are a common sight during warmer months. Their disappearance as colder weather arrives often prompts questions about their fate. These insects employ specific strategies to endure the winter, ensuring the survival of their species through a unique annual cycle.
The Annual Cycle and Winter’s Toll
Bumble bee colonies operate on an annual cycle, unlike the perennial colonies of honey bees. As autumn approaches, the existing colony, including the founding queen, worker bees, and male bees, gradually declines and perishes. This natural process sees the cessation of worker production and the eventual death of the entire summer colony.
During late summer and early fall, the colony’s focus shifts to raising new queens and males. Males leave the nest to mate with new queens. The old queen, having completed her reproductive cycle, and the worker bees, whose lifespan is limited, do not survive the onset of winter temperatures.
The Queen’s Winter Survival
The continuation of the bumble bee species relies solely on the new, fertilized queens, who are the only members of the colony to survive the winter. These young queens spend late summer and early autumn consuming nectar and pollen. This feeding allows them to build up substantial fat reserves, which are crucial for their survival during the long winter period.
Once they have accumulated sufficient energy, the new queens seek protected locations for hibernation. They enter a state called diapause, a form of dormancy where their metabolism slows considerably, allowing them to conserve energy. Common hibernation spots include loose soil, often burrowing 5 to 15 centimeters deep, under stones, in rotten logs, or beneath moss and leaf litter. Some queens also produce glycerol, which acts as an antifreeze within their bodies, aiding survival in cold conditions.
Emergence and New Beginnings
As spring arrives, the hibernating queen is roused from her diapause. Her first priority is to find early blooming flowers for nectar and pollen, replenishing the energy depleted during her long winter sleep. The pollen is particularly important as it provides the protein necessary for her ovaries to develop.
Following this initial foraging, the queen embarks on a search for a suitable nesting site. She often inspects abandoned rodent burrows, dense tussocks of grass, compost heaps, or even empty bird boxes. Once a site is chosen, she begins laying eggs and incubating them, initiating a new colony. The first offspring are female worker bees, who take over foraging, allowing the queen to focus on laying more eggs.