Exposure-altered repellency of vetiver oil against red imported fire ant workers (Hymenoptera: Formicidae).

Insect habituation is one of the problems in developing efficacious repellents. In an attempt to better understand the behavioral mechanisms of the red imported fire ant, Solenopsis invicta Buren, towards repellents, the behavioral changes of red imported fire ant workers with 2 days' exposure to sand-mixed vetiver oil at the concentration of2.5ul a.i./100g were observed using a residual film method in the laboratory. In the choice bioassays, vetiver oil exhibited a significant repellent effect to workers without prior exposure, but the repellency of vetiver oil to previously exposed workers decreased at low concentrations. The results suggested that for red imported fire ants, induced habitation resulting from experience may be one of the mechanisms that leads to a change in behavioral response to a repellent.