Host location behavior in a parasitoid of imported fire ants. Insect Behavior 17

Female parasitoids use a hierarchy of cues to locate suitable hosts. We con-ducted a series of field observations and experiments to examine host location behavior in Pseudacteon tricuspis Borgmeier, a phorid parasitoid of Solenop-sis invicta Buren worker ants. The parasitoids were frequently attracted to host workers at disturbed colonies, but were almost never attracted to host work-ers foraging at baits. When conspecific nonnestmate workers were introduced to baits, resulting in aggressive interactions, parasitoids appeared at the ma-jority of baits. Moreover, larger numbers of parasitoids appeared at baits to which greater numbers of nonnestmate workers had been added. Addition of nonnestmate workers to disturbed colonies resulted in increased numbers of parasitoids attracted. Pseudacteon tricuspis did not display a pattern of uni-form distribution at disturbed colonies but often was very abundant at some colony locations while absent or rare at nearby colony locations. Solenop-sis invicta workers release alarm pheromones in aggressive interactions with nonnestmates, and this substance is likely an important chemical cue that at-tracts P. tricuspis flies to host workers from a distance. KEY WORDS: host location; imported fire ant; parasitoid; pheromones; Phoridae