Chemical communication during foraging in the harvesting ant Messor capitatus (Hymenoptera, Formicidae)

Some aspects of the chemical communication system employed by the harvesting ant Messor capitatus during foraging were investigated in the laboratory. After locating a conspicuous food item the scouts return home dragging their gaster on the ground. Once inside the nest they run among nestmates and perform an excited motor display. Soon after, groups of workers rush out and move towards the food. Bioassays of different gland extracts showed that nestmates are activated and induced to leave the nest by substances from Dufour's gland. This gland was also found to be the source of the orientation-recruitment trails by which foragers reach newly discovered food sources. The bioassays showed that poison gland extracts are also active in inducing trail following. However, this response was accompanied by typical aggressive reactions by tested ants, suggesting that the poison gland is involved in alarm communication and recruitment towards a source of danger rather than in foraging activities. Some features of the Dufour's gland trail (such as its durability and lack of colony-specificity) are discussed with regard to the ecological requirements of this species.