Antennal Olfactory Responsiveness of the Texas Leaf Cutting Ant (Hymenoptera: Formicidae) to Trail Pheromone and its Two Alarm Substances

Electroantennograms (EAGs) were recorded from major workers, queens, and males of the Texas leaf cutting, Atta texana (Buckley) (Hymenoptera: Formicidae) in response to serial dilutions of two alarm substances, 2-heptanone and 4-methyl-3-heptanone, and its trail pheromone, 4-methylpyrrole-2-carboxylate. The lower EAG threshold for major workers relative to queens and males for both alarm substances correlated well with previously reported behavioral bioassays which showed workers to be most responsive to these odorants. Although laboratory behavioral bioassays showed minor workers, queens, and males to have a similar behavioral threshold for the trail pheromone, minor workers were more responsive to higher concentrations of the trail pheromone. However, EAGs revealed queens significantly more sensitive and responsive to the trail pheromone than the other castes. These seemingly enigmatic results are discussed with regard to A. texana biology and receptor physiology.