Colony behavior of the obligate social parasiteVespula austriaca (Panzer) (Hymenoptera: Vespidae)

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The obligate social parasite,Vespula austriaca (Panzer), after successfully usurping a colony, displayed overt physical dominance of the host workers,V. acadica (Sladen). Agonistic inquiline behavior such as mauling, chasing workers, and flailing were commonly observed during observations of 5 parasitized colonies. The parasites solicited workers more frequently than larvae for liquid nourishment, and commonly engaged in both typical and forced trophallaxis. Aggressiveness of the parasite was more intense during the early stages of colony occupation, and was less frequent and vigorous in the later stages of the colony. A brief, and probably intense, oviposition period occurred during the period of heightened parasite aggression. This species exhibited many activities similar to those of another vespine inquiline,Dolichovespula arctica (Rohwer), such as hyperactivity, gastral dragging, minimal nest construction and lack of colony defense, but also displayed some contrasting interactions. There was an absence of worker attraction to the inquiline, an inhibition of worker ovarian development by the parasite, and decreased aggression in later colony stages. It is hypothesized thatV. austriaca maintains colony control through an interplay of direct and forceful interactions with workers and by the use of pheromones.