Volatiles defenses of Amazon Azteca ants (repellent ants)

Azteca ants are widely distributed in the neotropics and have been utilized as natural insect repellent for centuries. Azteca oils provide natural defense against herbivores in mutualistic interactions between ants and their host trees. While chemical characterization of oil secretions revealed a composition dominated by iridoids and ketones, the volatile emissions from Azteca ants, and therefore the active gas-phase semiochemicals, remain uncharacterized. In this study, we determined the composition of volatile emissions from a sample of an Azteca ant nest near the Rio Negro in the central Amazon. We found Azteca emissions were composed of a blend of methyl cyclopentyl and methyl cyclopentenyl based volatiles previously identified in Azteca oil extracts as potent alarm pheromones. The ketone 6-methyl-5-hepten-2-one, which also waspreviously identified as a major component of the Azteca oil, was found to be the dominant volatile emitted. For the first time, we report emissions of the highly volatile ketones 2,3-butadione and acetoin from the Azteca nest. Our study has important implications for the better understanding of the ecology and defense strategies of Azteca ants in herbivore defense and provides a base for future commercial applications involving Azteca ant essential oils as natural insect repellents.