Electroantennogram and behavioral responses of the species of phorid flies, Pseudacteon spp., to alkylpyrazine analogs of alarm pheromone of red imported fire ant, Solenopsis invicta

Pseudacteon phorid flies are introduced parasitoids of imported fire ants, Solenopis spp.  Previous studies have demonstrated that phorid flies use semiochemicals released by fire ants, including venom alkaloids and alarm pheromones, to locate their hosts. Results from a recent study by our group show significant differences in the electroantennogram (EAG) and behavioral responses of the phorid fly, Pseudacteon tricuspis (Borgmeier) to the pheromone isomer and other alkylpyrazine analogs of the fire ant alarm pheromone. In this study, we present results of a comparative study of EAG and behavioral responses of three species of phorid flies (P.cultellatus, P. curvatus, and P.obtusus) to commercially available alkylpyrazine analogs of alarm pheromone of the red imported fire ant, S. invicta. First, we tested the EAG responses of P. cultellatus, P. curvatus, and, P.obtusus to the pheromone isomer (2-ethyl-3,6(or 5)-dimethyl pyrazine) and six related alkyppyrazine analogs. The most promising compounds were then selected for further testing in EAG and four-choice olfactometer bioassays. Results show significantly higher EAG and behavioral responses of females of the three phorid species to the pheromone isomer at the variouse doses tested (0.001, 0.01, 0.1, and 1 µg). The results confirm  the attraction of phorid flies to fire ant alarm pheromone.