Resources in the colony dump of Acromyrmex lobicornis (Hymenoptera: Formicidae) leaf-cutting ants influence their foraging preferences in the field

ALMA, A. MARINA; ARENAS, ANDRES; FERNÁNDEZ, PATRICIA; BUTELER, MICAELA

Congreso; XI Congreso Argentino y XII Congreso Latinoamericano de Entomología; 2022

As central place foragers, social insects incorporate resources from the surroundings into the nest.Once inside, resources provide colony-mates with information about the food sources being exploited.In leaf-cutting ants, information about the plants they use as a substrate for the symbiont fungus influ-ences foraging decisions. Thus, foragers reject initially accepted resources after experiencing their cuesin the waste dump of the colony. So far, changes in foraging preferences after learning from the dumpwere observed in small colonies of Acromyrmex ambiguus (Hymenoptera: Formicidae) under laborato-ry conditions. Here, we extended the study of such avoidance response using Acromyrmex lobicorniscolonies settled under natural conditions, where the diversity of available resources and the size andcomplexity of the nests could challenge ants’ abilities to learn information from the dump. We askedourselves whether colonies in nature learn to reject the resources ants experienced in the dump. To thisend, we estimated the size of the colonies and in turn, we added one oat flake onto the waste pile every100 ants. Avoidance response was measured for six weeks using different variables. On the one hand, wequantified the proportion of oat flakes accepted in a dual-choice test where we simultaneously offeredoat and corn flakes (as experienced and novel resources respectively) on the main trail, before and afteroat exposure to dump. On the other hand, we performed single-choice trials to compare the acceptancerate of oat flakes vs. corn flakes. Despite being suitable for the fungus and harmless to the ants, weobserved that the oat flakes were much less accepted 24h after being incorporated into the dump anddifferent from oat acceptance recorded in non-exposed colonies (control). The acceptance rate of oatflakes differed from that of corn flakes from 24h after exposure, and extended over the six weeks of theexperiment. We discussed if plant material that is discarded can provide relevant information on thesuitability of resources available in the environment.