Altruism simulation based on pheromone evaporation and its diffusion in army ant inspired social evolutionary system

Army ants perform the altruism, in which an ant sacrifices its own well-being for the benefit of another ants. Army ants build bridges using their own bodies along the path from a food to the nest. We developed the army ant inspired social evolutionary system which can perform the altruism. The system has 2 kinds of ant agents, `Major ant' and `Minor ant' and their ants communicate with each other via pheromones. The other ants can recognize them as the signals from the other ants. The pheromones evaporate with the certain ratio and diffused into the space of neighbors stochastically. If the optimal bridge is found, the path through the bridge is the shortest from foods to the nest. However, the simulation results may show two or more bridges. We propose the constructing method of the optimal bridge to define the probability for an ant to leave a bridge at a low occupancy condition of ants. The computer simulation results are described in this paper.