Usurpation Behavior of the Yellowjacket Social Parasite, Vespula austriaca (Panzer) (Hymenoptera: Vespidae)

Abstract

Collection dates of an uncommon yellowjacket social parasite, Vespula austriaca (Panzer) (Hymenoptera:Vespidae), in North America indicate this species emerges from hibernation and seeks established nests of the host [ V acadica (Sladen)] primarily after the emergence of the first host worker. Timing of usurpation attempts was investigated by experimentally staging contests between parasites and members of three different colony. stages (queen nest, queen-reared worker stage, larger postemergence colony). These usurpation attempts revealed no peaceful coexistence period with the host queen, but instead immediate aggressive invasion behavior. The host queen was the victor in nearly all encounters with the parasite during the queen nest stage. However, queen behavior changed after worker emergence and she no longer vigorously defended the colony. The intruding parasite killed a third of the worker force of the larger postemergence colony and drove the queen from the nest before physically dominating the remaining workers.