Only young fertilized queen hornets overwinter. The queens wake up in the middle of April, and in May they start the process of building up new colonies. In late May, the first workers hatch, and from there, the colony size quickly grows. In August, there are up to 5000-6000 members of the colony.
Until then, we see very little of the hornets. They are busy gathering wood pulp to the ever-growing nest and hunting insects to feed to the larvae. The nest is spherical, and built by a grayish paper substance. It is usually located in bushes or hollow timber, or it is built into a cavity in the ground or in a stone wall. Hornets often find suitable nesting sites in attics, cavity walls or outbuildings.
In the autumn, the hornet society stops working. The hornets no longer feed the larvae. They roam around on their own searching for sweet stuff, and at this time, the risk of getting stung by hornets is greatest at this time. During October, the workers and the queens die. The new, young queens seek sheltered places, for example insulation materials in an attic, where they can overwinter.