The bald-faced hornet (Dolichovespula maculata) is a social wasp belonging to the yellowjacket family. These insects follow an annual life cycle, meaning the vast majority of the colony dies off completely each year. This mass die-off, including all workers, males, and the original founding queen, is triggered by the changing seasons and the onset of cold weather. The colony exists only for one season, from spring until the first sustained low temperatures of late autumn or early winter.
The Annual Seasonal Timeline
The life cycle begins in the spring when a lone, fertilized queen emerges from hibernation. She establishes a small nest and raises the first generation of sterile female workers, who then take over nest construction and foraging. The colony population grows steadily through the summer, peaking at a few hundred individuals (100 to 400 workers) by late August or early September.
The end of the season typically occurs in late October or early November, coinciding with the first hard frost or sustained drop in temperature. While some nests in milder climates might persist longer, the colony’s functioning ceases once the environment can no longer support its metabolism and food supply.
The Mechanism of the Colony Die-Off
The colony’s fate is sealed when the founding queen switches egg production from sterile workers to fertile males and new queens in late summer. After these new reproductive members have emerged and left the nest to mate, the old queen ceases laying eggs altogether. This cessation of brood production is a significant factor in the colony’s decline, as the workers no longer have developing larvae to feed, nor do they receive the protein-rich secretions the larvae produce in return.
The remaining workers become vulnerable to the dropping temperatures because their insect physiology is not adapted for cold survival. Wasp activity, particularly foraging flights, becomes impaired when ambient air temperatures fall below 50 degrees Fahrenheit. As the weather cools further, the workers and the old queen are unable to sustain the internal temperature necessary for survival. They ultimately perish from a combination of starvation, cold exposure, or old age, with the first sustained freezing temperatures ensuring the death of any stragglers.
Survival and the Next Generation
The only members of the bald-faced hornet population that survive the annual die-off are the newly produced, fertilized queens. These young queens leave the established nest shortly after mating to seek a suitable, sheltered location for their winter survival. They do not remain in the old nest, which is abandoned once the workers have died.
The new queens enter a state known as diapause, which is a period of metabolic inactivity similar to hibernation in mammals. They seek out protected microclimates, often burrowing under loose tree bark, within soil debris, or finding refuge in structural voids, to wait for the return of warm weather. These overwintering queens have freeze-tolerance mechanisms, such as producing glycerol, a type of antifreeze protein, that lowers the freezing point of their bodily fluids. Each surviving queen will emerge the following spring, build a new nest from scratch, and begin the annual colony cycle anew, ensuring that the previous year’s nest is never reused.