(S)-2-Heptanol, the alarm pheromone of the stingless bee Melipona solani (Hymenoptera, Meliponini)

Timely defence response is critical in any highly social bee species. Chemical signalling is closely linked to this behaviour, and several pheromones have been discovered. In this work, we identified the pheromone of the stingless bee Melipona solani and evaluated the electrophysiological and behavioural response of the bee to the identified compound. We determined that the mandibular glands serve as the reservoir of the alarm pheromone. Because enantiomeric recognition has been scarcely examined, we performed bioassays and electroantennographic (EAG) studies to determine the role of chirality in pheromone recognition. We found that (S)-2-heptanol was the active compound involved in the alarm response of this species. Although we did not find (R)-2-heptanol in the mandibular gland extracts, bees responded to it in a similar way to the (S)-isomer and to a racemic mixture. The behavioural response of M. solani was flight, different from other Melipona species behaviour. We discuss these findings in an evolutionary and ecological framework.