Forager Distribution in Nectar Sources and Sucrose Acceptance Threshold within an Ant Colony

LOPEZ, M.A.; JOFRE, N; FALIBENE, A; JOSENS, R

Encuentro; 1st Latin American Meeting of Chemical Ecology; 2010

Chemical control in social insects has the restriction to use only alimentary baits. Almost all the urban ants collect sugar solutions as an important part of their diet. Thus, sugar is a common bait used in ant control. Some ant species present a wide range in worker sizes and foragers of different sizes participate in nectar collection. Different worker sizes involve diverse restrictions and limitations regarding intake respect to solutions of different concentrations. We analyzed how forager sizes relate with colony’s foraging organization and some of the underlying mechanisms that might operate. In field experiments, we found that workers of different sizes collecting for nectar are distributed according to sources productivity. Larger ants forage on nectar that is more concentrated or produced at higher flows. For laboratory experiments, we firstly developed a new protocol to record sugar acceptance threshold (SAT), which represents the lowest sucrose concentration at which an ant can distinguish between water and sucrose eliciting a licking response. It allows detecting differences in SAT under carefully controlled conditions using a wide range of concentrations in harnessed ants of different sizes. Results showed that large ants had a higher threshold than small ants when the colony was not sugar starved, but when the colony was longer starved, both small and large ants presented the same low threshold for sugar acceptance. These physiological variations between ants of different sizes can operate as a differential trigger in forager recruitment contributing to the distribution found in the field among nectar sources, which leads to a greater overall system efficiency.  Support by ANPCyT(PICT-2007-1319)