Ant colonies, and more generally, social insect societies, are distributed systems that, in spite ofthe simplicity of their individuals, present a highly structured social organization. As a result of thisorganization, ant colonies can accomplish complex tasks that, in some cases, far exceed the individualcapabilities of a single individual. Ants coordinate their activities via stigmergy, a form of indirectcommunication mediated by modifications of the environment. In other words, biologists have shownthat it is often sufficient to consider stigmergic indirect communication to explain how social insectscan achieve self-organization.