Hornets, members of the genus Vespa, are the largest and most recognizable of the social wasps, often differentiated from bees and other wasps by their robust body structure and seasonal life cycle. Unlike honey bee colonies, which are perennial and survive multiple years, hornet colonies in temperate climates are strictly seasonal. This means the entire colony, including the founding queen and all her workers, perishes within a single year, with only the next generation of queens surviving.
The Solitary Beginnings: Queen Emergence in Spring
The annual cycle begins in early spring when a single fertilized queen emerges from hibernation (diapause). She immediately searches for a suitable, sheltered location to establish a new colony, often choosing hollow trees, wall voids, or protected cavities. This initial phase requires the queen to perform all tasks alone, as she has no workers to assist her.
She gathers wood fibers from trees and weathered structures, chewing them with her mandibles and mixing them with saliva to create a paste. This material hardens into a durable, paper-like substance used to construct the “primary nest,” which consists of a small comb of hexagonal cells surrounded by a protective paper envelope. The queen then lays the first batch of eggs, which will develop into sterile female workers.
For the next few weeks, the queen is solely responsible for foraging for protein (mostly insects) to feed the developing larvae. This solitary labor is the most vulnerable period for the new colony, as the queen must divide her time between hunting, nest maintenance, and brood care. Once the first generation of workers emerges as adults, typically in late spring or early summer, the colony quickly transitions to a cooperative endeavor.
Peak Activity: Summer Colony Growth
The emergence of the first sterile female workers marks the beginning of the colony’s exponential growth phase. These workers immediately assume all responsibilities outside of reproduction, including foraging for food, gathering wood pulp for construction, and defending the nest. The founding queen, now relieved of her duties, remains inside to focus exclusively on laying eggs.
With a dedicated workforce, the nest expands rapidly throughout the summer, with workers adding multiple tiers of comb and enlarging the paper envelope. This division of labor allows the colony population to swell dramatically; European hornet colonies often peak at several hundred workers, while some species reach populations in the thousands.
The colony requires large amounts of protein (masticated insects) to fuel the growth of thousands of developing larvae. This intense period of activity ensures the colony reaches its maximum size by late summer, setting the stage for reproduction.
The Fatal Transition: Reproduction and Colony Decline
The queen shifts her egg-laying strategy, triggered by environmental cues like shortening day length and colony size. In late summer or early autumn, she begins to produce two new types of individuals: males (drones) and new, large females called gynes, who are the future queens. The males develop from unfertilized eggs, while the gynes are reared in specialized, larger cells and receive a richer diet.
Once the new reproductives mature, they leave the nest to participate in mating flights, often congregating with individuals from other colonies. The males die shortly after mating, having served their purpose. The newly fertilized gynes seek out protected locations to enter diapause.
Meanwhile, the old queen’s egg production slows and eventually ceases, leading to her death. The colony structure begins to fail without a continuous influx of new workers to replace those dying of old age and exhaustion. The remaining workers, no longer receiving hormonal signals from the queen, experience a behavioral change.
They shift their focus from hunting insects for the brood to seeking high-energy sugary substances for themselves. This results in the aggressive scavenging behavior often observed around human food sources in the fall.
The final demise of the colony is hastened by the onset of cold weather. Hornets, being cold-blooded insects, become lethargic as temperatures drop, making foraging impossible. The first sustained hard frost or prolonged cold snap signals the end, as the remaining workers starve or succumb to the cold. The abandoned nest is never reused and quickly falls into disrepair, completing the colony’s annual life cycle.
Surviving Winter: The Next Generation
The only members of the colony to survive the winter are the newly mated queens (gynes) who left the nest before the cold set in. These individuals seek out highly insulated microhabitats, such as loose tree bark, beneath leaf litter, in decaying logs, or within crevices in structures. They enter diapause, which allows them to conserve energy and endure months of freezing temperatures and lack of food. Upon emergence in the following spring, each surviving queen will single-handedly found a new nest and restart the annual cycle.