Mandibular gland chemistry of grass-cutting ants: species, caste, and colony variation.

The compositions of the alarm pheromones of two species of grass-cutting ant, Atta bisphaerica and A. capiguara, were examined, and caste and colony variations quantified. The pheromones of A. bisphaerica and A. capiguara were remarkably similar and were composed of a complex mixture of volatiles in which 4-methyl-3-heptanone and 2-heptanone were the most abundant compounds. Small but consistent intraspecific differences were found between the worker castes and between individual colonies. The results support the view that alarm pheromones are rarely species specific. The possible importance of intercolony variation is discussed.