Ant Lasius niger joining one-way trails go against the flow.

Social insects, such as ants, use various pheromones as their social signal. In addition, they use the presence of other ants for decision-making. In this study, we attempted to evaluate if individual decision-making is influenced by the complementary use of pheromones and presence of other ants. Ants were induced to form a one-way flow system. We found that when ants entered such a system at a right angle, they tended to move in the opposite direction of the one-way flow system. Interestingly, the target ants moved randomly in the experiments in which no ant and/or no pheromone trails were present. We also developed simulation algorithms and found that artificial ant foragers could reach a certain goal more often if they adopted the reverse run (similar mechanism found in ant experiments) over the forward run (moving in the same direction as their nestmates).