Hornet activity levels are closely tied to their surrounding environment, especially temperature. Their physiological processes are directly influenced by thermal conditions, providing insight into their behavior throughout the year.
Hornet Flight and Temperature Thresholds
As temperatures drop, hornets gradually become less active. Most species exhibit sluggishness and reduced activity when temperatures fall below approximately 10°C (50°F). Below this threshold, their ability to fly effectively is significantly impaired, often ceasing entirely. While activity decreases gradually, some species, such as yellowjackets, can maintain some activity until temperatures approach freezing. Even these species experience a marked reduction in their foraging and overall movement.
The Science Behind Cold Inactivity
Hornets are ectotherms, meaning their internal body temperature is largely determined by the external environment. When ambient temperatures decrease, their body temperature drops, which in turn slows their metabolic rate. This metabolic slowdown directly impacts their movement and various biological processes.
Lower temperatures also impair muscle function, particularly the flight muscles. Cold can lead to chill coma, a reversible state of paralysis where muscle fibers undergo depolarization. This physiological change reduces their ability to coordinate movement.
Enzyme activity, essential for nearly all biological reactions, also decreases significantly in colder conditions. Cold also causes lipids in cell membranes to rigidify, further compromising cellular functions.
Hornet Survival in Winter
When sustained cold temperatures arrive, most of the hornet colony perishes. This includes all worker hornets, males, and the old queen. Their demise is a result of both freezing conditions and a dwindling food supply.
The future of the species relies solely on newly mated queens, the only members of the colony to survive the winter. These fertile queens seek out sheltered locations to overwinter, such as beneath tree bark, within logs, in the soil, among leaf litter, inside woodpiles, or in protected crevices. They enter a dormant state, known as diapause, where their metabolism slows significantly, and their body temperature matches that of their surroundings. During this period, the queens remain inactive, consuming minimal energy.
Once spring arrives and temperatures rise, these overwintered queens emerge to establish new colonies, building small nests and laying the first eggs that will hatch into new worker hornets. Hornets rarely reuse their old nests for hibernation or for starting new colonies the following year.