Fig. 7. Simulation results. Distribution frequency of the size of the groups of successive ants travelling in the same direction at the level of the line between the bottleneck and the entrance on the nest side of the bridge when the simulations were run with a flow of ants entering the bottlenecks of the bridge equal to 0.5 ants per time step, corresponding to the flow measured in the experiments on a 3 mm bridge. The simulations were run with and without implementing a cooperative rule between following ants. For explanations on the random distribution, see Fig. 5.