Yellow jackets are common social wasps, recognized by their black and yellow markings. Their presence is noticeable during warmer months. As temperatures change with the seasons, so does their behavior and activity. Understanding how temperature influences yellow jackets is important for comprehending their seasonal patterns.
When Yellow Jackets Slow Down
Yellow jackets are cold-blooded insects, meaning their body temperature is directly influenced by the ambient environment. Consequently, their activity levels are tightly linked to temperature fluctuations. When temperatures drop, their metabolism slows, leading to reduced activity.
Individual yellow jackets become sluggish when temperatures fall below approximately 50°F (10°C). This reduction in activity means they are less likely to engage in their usual foraging and defensive behaviors. Foraging largely ceases when temperatures remain below 45-50°F (7-10°C).
Sustained cold temperatures can be lethal for individual worker yellow jackets. They cannot survive prolonged exposure to temperatures at or below 45°F (7°C) for 5-7 days. Freezing temperatures, below 32°F (0°C), directly kill individual workers exposed to the elements. While some species may huddle for warmth within a nest, most workers eventually die from the cold.
How Cold Affects the Colony
As autumn progresses and temperatures decline, the entire yellow jacket colony undergoes a natural seasonal decline. Worker yellow jackets, males, and the old queen die off with the onset of cold weather. In temperate regions, the entire yellow jacket nest does not survive the winter. Abandoned nests decompose rapidly and are rarely reused.
The survival mechanism for yellow jackets through the winter relies on newly mated queens, also known as gynes. These fertilized queens seek sheltered locations to overwinter, such as hollow logs, tree stumps, under bark, leaf litter, or soil cavities. They also find shelter in human-made structures like attics or wall voids. During this period, queens enter a state similar to hibernation, lowering their metabolic rate and conserving energy.
Newly mated queens possess adaptations, such as “antifreeze” proteins, which help them tolerate freezing conditions by preventing ice crystals from forming inside their bodies. In the spring, as temperatures rise, these hibernating queens emerge. Each surviving queen then searches for a suitable site to begin a new colony, restarting the annual life cycle.
Other Factors Influencing Yellow Jacket Activity
While temperature is the primary determinant of yellow jacket activity, other environmental factors also contribute to their seasonal patterns and decline. As temperatures drop in the fall, there is a natural decrease in their primary food sources, such as other insects and nectar. This scarcity of food can lead to increased scavenging behavior.
Shorter daylight hours also reduce the time available for foraging. These environmental shifts, combined with the natural end of the colony’s annual life cycle, contribute to the reduction in yellow jacket activity observed in cooler months. Most yellow jackets naturally die off by winter.