Nest refuse extract deters ant herbivory

Abstract

Leaf-cutting ants (LCA) try to reduce the risk of contamination in their colonies by avoiding contact with their nest refuse (NR), as it can harbor substances harmful to them and their symbiotic fungi. Here, we tested whether an aqueous extract with 10% (vol/vol) of NR of the leaf-cutting ant Atta opaciceps Borgmeier (Hymenoptera: Formicidae, Attini) causes a deterrent effect. We placed leaves of Hibiscus rosa-sinensis L. (Malvaceae) sprayed with NR extract or distilled water (control) in the foraging areas of 12 colonies -eight colonies of A. opaciceps and four of Atta sexdens (L.) -for 60 min, on three consecutive days. The fresh weight of remaining leaf fragments between treatments was compared using linear-mixed effect models. Leaf consumption was significantly lower in the presence of NR extract for 48 h, indicating that the NR odor impregnated in the leaves may have been the responsible factor for the deterrence. Further studies are needed to establish a deterrent extract with a broad spectrum and lasting effect on plants, and to better understand the mechanisms involved in deterrence.