Yellow jackets receive their common name from their typical black and yellow color pattern. They are worldwide in distribution with about 16 species occurring in the United States.
Adult workers about 3/8-5/8″ (10-16 mm) long depending on the species, with their respective queens about 25% longer. Abdomen usually banded with yellow and black, several species with white and black, and 2 northern species also marked with red.
Yellow jackets are social insects and live in nests or colonies. The adults are represented by workers which are sterile females, queens, and males which come from unfertilized eggs and usually appear in late summer.
Typically, only inseminated queens overwinter and do so in sheltered places. In the spring, she uses chewed-up cellulose material to build up a paper carton nest of a few cells which will eventually consist of 30 to 55 cells covered by a paper envelope. One egg is laid in each cell and the queen feeds the developing larvae arthropod protein material and nectar. After about 30 days, the first 5 to 7 workers emerge and shortly thereafter take over all the work except egg laying. The nest will eventually consist of a number of rounded paper combs which are open ventrally and attached one below another, and are usually covered with a many-layered paper envelope. Nest size varies from 300 to 120,000 cells, averaging 2,000 to 6,000 cells, and usually contains 1,000 to 4,000 workers at its peak. Later in the season, larger reproductive cells are built in which queens will be reared; males are usually reared in old worker cells. The colony is then entering the declining phase. The newly emerged queens and males leave the nest and mate. Only the inseminated queens hibernate and survive the winter. The founding queen, the workers, and the males all die.
Depending on the species, the overwintered queen will usually select either a subterranean or aerial nesting site. Most of the pest species are ground nesting. However, the German yellow jacket usually nests in buildings in the United States, the western yellow jacket occasionally nests in buildings, and the aerial yellow jacket commonly attaches its nest to shrubs, bushes, houses, garages, sheds, etc.
Those nesting in the ground typically select areas bare of vegetation or else clear an area around the entrance. There are nest entrance guards to protect the colony. Yellow jackets are very slow to sting unless the nest entrance is approached and then they are quite aggressive. Each can sting a number of times, inflicting much pain. Some people become hypersensitive to their stings and future stings can become life threatening. Those nesting in or on buildings are only a problem when the nest or nest entrance is located near human activity. Overwintering queens may enter the living space during the winter seeking warmth, or in the spring when they are looking for a nest site or just trying to get back outside.