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Yellowjacket adult
(John Obermeyer, Purdue University)
Common Name: Yellowjacket - adult

Scientific Name: Hymenoptera: Vespidae: several species

Status: painful and potentially lethal sting; otherwise beneficial

Damaging Stage: adult

Biology: Yellowjackets are smaller than their close relatives-hornets and paper wasps—but they occur in larger colonies, sometimes with several hundred workers. They are usually bright yellow with black dots and stripes across their abdomens. Immature yellowjackets are white, grublike larvae. They are rarely ever seen unless the nest is torn open.

A new queen leaves the nest during the fall, mates, and passes the winter under leaf litter or the bark of trees. In the spring, the queen starts a colony by building a gray paper nest, usually underground or in a wall void or other cavity, in which she lays eggs and cares for the developing larvae. Once her first workers emerge, they take over the nest building, foraging and defense duties for the colony. The queen remains inside the nest and focuses primarily on reproduction. By late in the season the nest can become very large and be home to many yellowjackets. There is only one generation per year.

Injury: While yellow jackets can sting and harm humans, they are an invaluable source of pest control in gardens and on farms. Yellowjackets are predators of crop-damaging pests such as flies and caterpillars. When defending themselves or their nests, however, yellowjackets can become very aggressive and may sting repeatedly. The sting is always painful but even can be life-threatening, depending on an individual’s skin reaction to the venom.

Action Threshold: A nest constructed on or near a home can be a potential threat to people. If the nest is in a place where there is a high likelihood that it will be interfered with by people, chemical controls are recommended. Nests well away from human activity should be left alone because of the beneficial nature of yellowjackets.

Management: Yellowjackets often forage in and around trash receptacles or ripened fruits and vegetables and thereby come into contact with people. Simply removing or temporarily relocating the source of their attraction will be enough to reduce human/yellowjacket encounters. Several insecticides can be used to treat yellowjacket nests.