Specificity of laboratory trail following by the argentine ant, Iridomyrmex humilis (Mayr), to (Z)-9-hexadecenal, analogs, and gaster extract

In laboratory trail-following bioassays of Argentine ant workers, Iridomyrmex humilis (Mayr), the geometric isomer, (E)-9-hexadecenal, of the trail pheromone component (Z)-9-hexadecenal elicited insignificant trail following as did the potentially more stable formate analogs, (Z)-7-tetradecenyl formate, (E)-7-tetradecenyl formate, and tetradecyl formate. Further, in direct choice tests, workers showed no preference for gaster extract trails (0.002 ant equiv/cm) over trails of (Z)-9-hexadecenal (0.2 ng/cm). Moreover, a 10-fold increase in synthetic trail concentration to 2.0 ng/cm caused (Z)-9-hexadecenal trails to be significantly preferred over gaster extract trails by trail-following ants.