GREENE, M. J.; GORDON, D.M.; University of Colorado at Denver; Stanford University: Cuticular hydrocarbons act as cues in the interaction network regulating harvester ant task allocation

Social insect colonies perform a variety of tasks, such as foraging, nest construction and brood care. Task allocation is the process that adjusts the numbers of workers performing each task in a way appropriate to current conditions and colony needs. Task allocation is a complex dynamical system that operates without central control. No colony member directs the behavior of others, and none can assess the global needs of the colony. A central question about task allocation is how it arises from individual response to local information. Our experiment focused on the interaction between patrollers and foragers of the red harvester ant (Pogonomyrmex barbatus). Patrollers scout the foraging area each morning and stimulate the emergence of foragers as they return to the nest: inhibiting the flow of patrollers returning to the nest inhibits foraging activity. We employed a bioassay that mimicked the return of patrollers into the nest after we inhibited foraging. Previous work showed that the task a harvester ant worker performs depends on the rate at which it encounters workers of other tasks. Further, another study showed that members of each task share task-specific cuticular hydrocarbon profiles on the surface of their cuticles. We show here that the interaction network that drives harvester ant task allocation is based on the perception of task-specific cuticular hydrocarbons during brief antennal interactions between workers of different tasks. In the experiment, the return of patroller-specific hydrocarbons to nests was sufficient to rescue foraging activity.