The bald-faced hornet, often mistaken for a true hornet, is actually a large species of aerial yellowjacket known for its black and white markings. This insect follows a strictly annual life cycle, meaning the entire colony does not survive the winter. A bald-faced hornet colony begins and ends within a single year, resulting in the dispersal and death of the vast majority of its members every autumn. This yearly cycle determines when the nest becomes inactive and the insects depart.
The Seasonal Timing of Colony Growth
The annual cycle starts in early spring, typically around April or May, when a single fertilized queen emerges from her overwintering location. She seeks a suitable, sheltered site, such as a tree branch, shrub, or under the eaves of a building, and begins constructing a small starter nest from chewed wood fibers mixed with saliva. This initial phase requires the queen to perform all duties, including foraging, nest building, and caring for the first brood of eggs.
Once the first generation of sterile female workers hatches, usually in late spring, they take over foraging and expanding the nest. This transition marks the beginning of the ergonomic stage, where the queen focuses solely on laying eggs. The colony enters a period of rapid growth through June, July, and August, with the nest swelling into its characteristic football or pear shape, often reaching up to two feet in height.
By the end of the summer, the colony reaches its maximum size and activity, commonly housing between 100 and 400 workers. During this peak period, the hornets are most visible and become highly protective of their nest structure. The high level of activity and number of workers make late summer the time when encounters and defensive stinging behavior are most likely.
Seasonal Dispersal: When the Workers Die
The dispersal of the colony begins in late summer and early autumn when the queen shifts her egg production to focus on new reproductive individuals. Instead of sterile workers, she lays eggs that develop into unfertilized males (drones) and new queens. These reproductives consume the colony’s resources, growing to maturity before leaving the nest to mate with individuals from other colonies during mating flights.
Once mating is complete, the males die shortly thereafter. The newly fertilized young queens search for protected locations—such as hollow logs, under bark, or in wall voids—where they will hibernate for the winter. This departure signals the end of the original colony, as the old queen and the remaining sterile workers quickly enter a decline.
The final factor ensuring the abandonment of the nest is the onset of cold weather. The remaining workers and the old queen die naturally due to old age or are killed by the first hard frosts and sustained cooling temperatures of late autumn. Depending on the climate, this mass die-off and final dispersal of the colony typically occurs from late October through early December, leaving the nest inactive for the winter.
Fate of the Abandoned Nest
Once the cold weather has passed and the colony has dispersed, the large, gray, paper structure is abandoned. The nest is constructed from cellulose fibers, essentially paper, which is easily degraded by winter weather and moisture. Bald-faced hornets strictly adhere to an annual cycle and never reuse an old nest.
New queens build a fresh nest each spring to prevent the buildup of parasites and disease. The abandoned nest is safe to approach and remove once sustained freezing temperatures have ensured the death of any remaining individuals. While the structure may remain intact for a couple of years, removal is generally recommended only after the onset of winter to ensure no hornets remain inside.