Nest may contain from 300 to over 100,000 cells. Only fertilized queens live over the winter in most species. Yellowjackets are only a problem when people get close to their nest entrance without knowing it. These wasps can sting repeatedly, and become very aggressive when defending their nest. Their sting is usually very painful and humans can develop a true allergy to their venom.
Any later sting can be life threatening.
Control of yellow jackets should only be undertaken by properly trained and equipped professional pest management personnel. Control is best done at night or late evening. The German Yellowjacket and the Western Yellowjacket often nests in building, and the Aerial Yellowjacket often attaches its nests to bushes or buildings. As nests in buildings are expanded, the Yellowjackets often chew through into living or work areas, posing a direct threat to occupants. After a pest technician has controlled all the adult insects from a nest in a building, the nest itself should be removed as completely as possible.