Naïve ants reach a food source quicker when encountering returning ants

Pheromone guidance of ant foraging activity is well described, but less is known about how the presence of inward ant traffic on the trail affects the behavior of naive nestmates and if these influences are dependent or independent of pheromone signaling. Here, we examined whether the flow of foraging Lasius niger ants coming from a feeder influences the movements of naive nestmates traversing a pheromone trail. We used a device that permitted individual ants to travel from the nest to a feeder via a single bridge under four conditions; unidirectional inward ant traffic, where naive foraging ants contacted only colony members returning from the feeder along a pheromone trail; foraging following a pheromone trail without ant traffic; foraging with neither a pheromone trail nor ant traffic; foraging with bidirectional ant traffic, where naive ants encountered other ants moving both toward the feeder and returning on the pheromone trail. The time required by inexperienced ants to reach the feeder was shorter in the unidirectional condition (returning from the feeder) than the other three conditions. These findings suggest that specific cues can regulate the movement of pheromone-guide foraging by ants.