Caryophyllene and caryophyllene epoxide are two terpenoids found in neotropical plants and known to be deterrent to leafcutter ants. To estimate the variation in deterrent activity of these compounds toward the generaAtta andAcromyrmex, behavioral bioassays were conducted over a range of concentrations. The responses of four captive colonies ofAtta cephalotes and two captive colonies ofAcromyrmex octospinosus, all from a single locality in Costa Rica, were studied. Although specific patterns of deterrency differed in the two genera, in both cases caryophyllene epoxide concentrations of 0.70 mg/g or greater, and caryophyllene concentrations of 7.0 mg/g or greater, significantly deterred the harvest of potential substrates. Individual colonies within each genus did not differ significantly in their responses to caryophyllene epoxide. The mean response of the two genera to caryophyllene epoxide differed significantly, but responses to caryophyllene did not.Acromyrmex octospinosus was more sensitive to low concentrations and less sensitive to high concentrations of caryophyllene epoxide than wasAtta cephalotes.