Hornets are ectothermic, meaning their body temperature is directly influenced by the surrounding environment. This makes them highly susceptible to temperature changes, which dictate their activity levels and survival. Understanding their response to varying temperatures provides insights into their seasonal behavior.
When Hornets Slow Down
Hornets begin to show signs of inactivity as temperatures drop, typically when the air falls to around 7°C to 10°C (45°F to 50°F). Below this range, their metabolic processes slow considerably, causing them to become sluggish and less mobile. This decrease in temperature affects the efficiency of their muscle function and enzyme activity, making sustained flight and foraging difficult.
When hornets become inactive, they exhibit reduced flight, diminished foraging efforts, and a general decrease in overall activity. Their aggression also tends to lessen in cooler conditions, making them less prone to stinging unless directly provoked. This physiological slowdown is a natural response to cold, allowing them to conserve energy as external conditions become less favorable. Hornets may enter a dormant, hibernation-like state during prolonged periods of cold.
How Hornets Endure Winter
With sustained freezing temperatures, the vast majority of the hornet colony, including worker hornets and males, perishes. Their paper nests, which offer limited insulation, are abandoned and not reused in subsequent years. The survival of the species through winter relies solely on newly mated queens.
These fertilized queens depart from the nest in late summer or early fall to seek out sheltered locations where they can safely overwinter. Common overwintering sites include protected spots under tree bark, within leaf litter, inside hollow logs, in crevices, or even in structures like attics. During this period, the queen enters a state of dormancy, known as diapause, where her metabolism slows drastically. This allows her to conserve energy and survive without food until warmer temperatures return in the spring, at which point she emerges to establish a new colony.
What Cold Weather Means for Hornet Encounters
Knowledge of how temperature affects hornet activity can influence interactions with these insects. In cooler weather, hornets are less aggressive and active, which can make late fall or early spring a potentially safer time to address abandoned nests, though caution should always be exercised. The threat posed by active hornet nests diminishes considerably as cold weather sets in and the colony naturally dies off.
While worker hornets are largely absent in winter, dormant queens might occasionally be found in sheltered areas. These hibernating queens are not a threat unless directly disturbed from their resting state. As spring approaches and temperatures rise, newly emerged queens will begin the process of building new nests. Being aware of this cycle can prompt individuals to check for new nesting activity around their property during the warmer months.