DELAYED AVOIDANCE OF PLANTS IN FORAGING L EAF- CUTTING ANTS IS TRIGGERED BY VOLATILES PRESENT IN THE NEST REFUSE CHAMBER

A. ARENAS; F. ROCES

Encuentro; The 3rd CENTRAL EUROPEAN SEC TION MEETING of the INTERNATIONAL UNION FOR THE STUDY OF SOCIAL INSECTS; 2013

Decision making in foraging leaf-cutting ants is not simply the result of the workers´ preferences, but is also influenced by the state of their symbiotic fungus as an additional informational center. Foragers can avoid certain plant species if they have been proven to be harmful for the fungus, albeit harmless for themselves. In response to the deleterious effects on the fungus, foragers interrupt harvesting of these leaves leading to delayed rejection, a phenomenon that involves long-lasting avoidance learning and that initiates soon after the introduction of the noxious substrate into the fungus garden. We found evidence that avoidance response is mediated by the presence of the substrate-related cues at the refuse chamber of the nest, where ants deposit the waste. By exchanging the refuse chambers of subcolonies that foraged on fungicide-infiltrated leaves and non-treated subcolonies, foragers from non-treated groups were able to reject the leaves the other group experienced as noxious. Moreover, the mere presence of inert-paper disks added with neutral odors in the refuse chamber was enough to convey information about the unsuitability of the substrate: foraging ants rejected those substrates smelling to the odors that scented the refuse chamber. Interestingly, the same odors that induced rejection when offered in the refused chamber turned out to be preferred if they were initially added into the fungus garden. We suggest that leaf-cutting ants decide to accept certain plants and reject others also based on local olfactory information obtained within the nest environment.