Trail-following responses ofTapinoma simrothi (Formicidae: Dolichoderinae) to pygidial gland extracts

Summary The pygidial (anal) gland was found to be the source of trail pheromone in the antTapinoma simrothi. Bioassays conducted with fractionated pygidial gland secretion indicated that the fraction containing iridodials and iridomyrmecin is responsible for the trail pheromone activity. Thus workers ofT. simrothi may utilize the same glandular exudate for alarm and trail following. At high emission rates from a point source, the ants responded in alarm, e.g., rushed to the source with open mandibles and raised abdomen. When concentrations were low and drawn as a line, the ants followed the secretion calmly. Trails ofT. simrothi are long-lived, having a biological half-life of 10 to 19 days. Quantitative studies of the evaporation rates of the iridodials by gas chromatography resulted in a half-life of 11 days, agreeing with the biological data. The implications of the use of the same glandular secretion for alarm and food recruitments are discussed.