Trail communication in the ant Megaponera foetens (Fabr.) (Formicidae, Ponerinae)

The African ponerine ant Megaponera foetens conducts well organized group raids on termites. Observations of raids in western Africa, together with laboratory experiments, confirm previous reports that recruitment is based on a scout system and trail pheromones. One component of the trail signal derives from the poison gland. We discovered a second trail pheromone which originates from the pygidial gland. The latter secretions have a more powerful recruitment effect whereas poison gland secretions contain a much longer-lasting orientation cue. The secretions of the sternal gland, Dufour's gland and hind gut contents do not elicit trail-following. The long bristles surrounding the tip of the gaster are innervated and probably serve as mechano-receptors during trail-laying. No evidence could be found that the conspicuous stridulatory sounds produced by the ant columns serve intraspecific communication. In the field, stridulation by raiding ants was observed exclusively as a response to disturbance. In the laboratory, strong vibrations of the ground as well as air currents elicit stridulation. Air/CO₂ mixtures are significantly more efficient in releasing stridulation compared to pure air. We suggest that these sounds are aposematic warning signals aimed at potential vertebrate predators.