When many wasps appear together, it often leads to the question of why they are “swarming.” Unlike honeybees, which typically swarm as a method of colony reproduction and relocation, social wasps generally do not exhibit this specific behavior for the same purpose. Instead, large gatherings of wasps are usually aggregations driven by various needs and stages in their life cycle. This article explores the different reasons behind these collective wasp behaviors.
Understanding Wasp Aggregations
Wasp aggregations refer to instances where a significant number of individuals from a wasp colony, or even multiple colonies, converge in one area. Social wasps, such as yellowjackets, hornets, and paper wasps, live in organized colonies with a queen, sterile female workers, and male wasps. These colonies operate on an annual cycle, beginning with a queen in spring and typically concluding with the colony’s decline in winter. The collective behaviors observed in wasps are connected to the colony’s growth, resource needs, and reproductive cycle.
Throughout the spring and summer, a wasp colony expands as the queen lays eggs and workers emerge to forage, build, and maintain the nest. As the season progresses into late summer and autumn, the colony reaches its peak size, and new reproductive individuals are produced.
Primary Reasons for Wasp Gatherings
Several distinct situations can cause wasps to gather in large numbers, often misinterpreted as swarming.
One common reason is defensive aggregation. Wasps will vigorously protect their nest if they perceive a threat, especially as the colony grows in late summer and early autumn. If a nest is disturbed, workers will emerge en masse, exhibiting aggressive behaviors like buzzing loudly and flying directly at perceived intruders to defend their home. This coordinated defense protects the queen and brood.
Wasps also form foraging aggregations when they locate a rich food source. As natural food supplies, such as insect prey, become scarcer in late summer and fall, wasps increasingly seek out sugary substances. This can lead to many individual wasps converging on sources like fallen fruit, sugary drinks, or picnic areas. While these gatherings involve many wasps, they are typically focused on resource collection rather than aggression, unless the food source itself is threatened.
Reproductive gatherings and dispersal occur at the end of the colony’s annual cycle. In late summer and fall, the queen begins to produce new queens and male wasps. These new reproductive individuals will leave the natal nest to mate. Males may form loose aggregations, sometimes in the hundreds, as they await the emergence of new queens for mating. After mating, the new queens seek sheltered places to overwinter, while the males and the old colony typically perish with the onset of colder weather.
Hibernation aggregations occur when newly mated queens seek overwintering sites. While often solitary, queens of some species may gather in protected locations like wall voids, attics, or hollow trees to survive the winter months. During this period, their metabolic rate slows significantly, allowing them to endure cold temperatures until spring. These gatherings are passive, as the queens are in a dormant state.
Distinguishing Different Wasp Behaviors
Identifying the type of wasp gathering helps understand their behavior and potential risk.
The location of the wasps is a primary indicator. If wasps are concentrated around a specific opening or structure, especially in a sheltered area, it might indicate a nest and thus defensive behavior if disturbed. Conversely, a gathering around spilled food or beverages suggests a foraging aggregation. Queens seeking hibernation spots may be found in quiet, protected crevices, often in or near human dwellings, particularly in the fall.
The behavior of the wasps offers further insight. Wasps involved in defensive aggregations near a nest will appear agitated, flying erratically, darting towards disturbances, and may exhibit increased buzzing. Foraging wasps, while numerous, are generally focused on the food source and are less aggressive unless directly provoked. Wasps dispersing for reproduction or seeking hibernation sites in the fall may appear less coordinated in their flight patterns or move slowly, especially during cooler temperatures.
The time of year is also a significant factor. Defensive behaviors and foraging aggregations are most pronounced in late summer and early fall when colonies are at their largest and food resources become more limited. Queens seeking hibernation sites are typically observed in the late fall as temperatures drop.