Learning through the waste: olfactory cues from the colony refuse determine plant preferences in foraging leaf-cutting ants

F. ROCES; A. ARENAS

Villasimius

Simposio; ESITO XV_European symposium for insect taste and olfaction; 2017

">Leaf-cutting ants are polyphagous herbivores that show distinct preferences in thechoice of plants as substrate for their fungus. Foragers are known to reject previouslyaccepted plants if they prove to be unsuitable for their symbiotic fungus onceincorporated into the nest, a phenomenon that involves olfactory avoidance learning.Inside the nest, waste particles removed from the garden likely contain cuesoriginating from both the unsuitable plant and the damaged fungus. We investigatedwhether leaf-cutting ant foragers learn to avoid unsuitable plants solely througholfactory cues available at the colony dump. We fed subcolonies of Acromyrmexambiguus privet leaves treated with a fungicide undetectable for the ants, collectedlater the produced waste, and placed it into the fungus chamber of naïvesubcolonies. In individual choice tests, naïve foragers preferred privet leaves before,but avoided them after waste was given into the fungus chamber. Evidence on theinfluence of olfactory cues from the waste on decision making by foragers wasobtained by scenting and transferring waste particles from subcolonies that had beenfed either fungicide-treated or untreated leaves. In choice experiments, foragers fromsubcolonies given scented waste originating from fungicide-treated leaves collectedless sugared paper disks smelling to it, as compared to foragers from subcoloniesgiven scented waste from untreated leaves. Results indicate that foragers learn toavoid plants unsuitable for the fungus by associating plant odours and cues from thedamaged fungus that are contingent in waste particles. It is argued that olfactorycues at the dump enable foragers to predict the unsuitable effects of plants even ifthey had never been experienced in the fungus garden, and that waste particles maycontribute to spread information about noxious plants for the fungus within thecolony.