Olfactory responses of Pseudacteon tricuspis Borgmeier (Diptera: Phoridae) to alarm pheromone and venom alkaloids of Solenopsis invicta Buren (Hymenoptera: Formicidae)

Pseudacteon tricuspis Borgmeier (Diptera: Phoridae) is a parasitoid of red imported fire ants, Solenopsis invicta Buren (Hymenoptera: Formicidae). Results from previous studies showed that attraction of P. tricuspis to S. invicta workers is mediated, at least in part, by host venom alkaloids. It has also been suggested that fire ant alarm pheromone may play a role in this host-parasitoid interaction. This study was conducted to investigate the behavioral response of P. tricuspis to fire ant alarm pheromones and venom alkaloids in four-choice olfactometer tests. The results confirmed the attraction of P. tricuspis to physiologically relevant doses of fire ant venom alkaloids and to the alarm pheromone alone. However, the flies were significantly more attracted to a treatment combining the alarm pheromone and venom alkaloid than to either as separate treatments. The results are discussed in relation to the behavioral ecology and host location behavior of phorid flies.