Glandular sources of recruitment, trail, and propaganda semiochemicals in the slave-making ant Polyergus rufescens

Abstract

The chemical sources involved in raiding activities of the slave-making ant Polyergus rufescens were investigated in the laboratory. In particular, we identified the sources of substances the raiding workers employ to convey information to nestmates and to disrupt reactions by defending workers during host nest invasion. Different secretions were offered to the dulotic ants on the tip of a blotting paper strip inserted a few centimetres into the nest entrance. The Dufour's gland secretion induced the characteristic mass exit from the nest and is likely the source of a recruitment signal. Moreover, laboratory tests with secretions from different anatomical structures revealed that the trail signals for homing raiding workers are conveyed by their hindgut contents released during the outbound trip. Finally, to ascertain if P. rufescens raiding workers use “propaganda” pheromones, the behavioural response of the Formica (Serviformica) cunicularia host workers to different secretions of the slave-makers was investigated. Only mandibular secretions caused the typical panic reactions shown by residents at the moment of nest invasion. This probably facilitates both nest invasion and brood sacking by raiding workers.