European hornets are social wasps which form colonies that live for one year. European hornets like to build their paper nests in hollow trees, barns and out buildings. However, they will also nest inside the walls, attic or chimney of buildings. Nests may also be constructed on the sides of buildings. Like yellowjackets and bald-faced hornets, European hornets aggressively defend their colony if it is disturbed. Loud vibrating noises from lawnmowers and leaf blowers can cause hornet workers to sting people and pets. Colonies of European hornets may contain several hundred workers.

Removing their nest is the only to effectively eliminate a hornet colony. This should only be done by an experienced professional. The danger of stings is considerable. Proper protective clothing and equipment are required.