ON THE TERRITORIAL BEHAVIOR OF FIELD COLONIES OF THE LEAF-CUTTING ANT ATTA-LAEVIGATA (HYMENOPTERA, MYRMICINAE)

The adaptative value of the territorial pheromone in leaf-cutting ants was investigated by studying the territorial behaviour of Atta laevigata in the field through a 2-yr-long observation period of four neighbouring adult nests in a pine tree plantation in Estado Monagas, Venezuela. Workers were found to secrete a colony-specific pheromone around their nest and along trunk trails. The extent to which ants marked the trail depended on the quality of the available food. This pheromone stimulated the aggressiveness of the resident workers and induced transport behaviour toward intruders. Its sole perception induced alarm in intruders, which, when encountering a resident worker, adopted a characteristic submissive posture. The same alarm behaviour was also observed among conspecifics, though without the same level of aggressiveness, when workers from one mound were introduced to territories of another mound of the same nest. Territory recognition depended simultaneously on visual and chemical cues, allowing the workers to orientate towards the nest mound they exited. Results suggest a double function for the territorial pheromone: to repel intruders from other colonies and to orientate workers on their way back to the nest. © 1990.