Application of computational stigmergy to hotspot characterization through data provided by location-based social networks
Definition of stigmergy in nature
“Stigmergy is a communication method used in decentralized systems by which the individuals of the system communicate with each other by modifying the surrounding environment. Stigmergy was initially observed in
nature; for example, ants communicate with each other leaving a trace of pheromones, so a colony of ants is an example of a stigmergic system. Another common example is that of the construction of termite nests. Termites also use pheromones to build very complex structures, following a simple decentralized set of rules. Each insect digs a ball of mud from its environment, covers it with pheromones, and leaves it on the ground. Termites are attracted to the pheromones of individuals of the same termite mound and then deposit their balls of mud next to those already deposited. Over time this behavior leads to the construction of pillars, arches, galleries and chambers. ” 
The pheromone trace is an indirect signal left in the environment for other ants, as well as others
they can follow it to find a resource. The pheromone trace dissipates over time, disappearing after
a lot of time. By analyzing the behavior of a single ant its contribution to the community is not
clear, because it acts and makes decisions independently, and apparently without interest in the others
ants. But by analyzing the whole of the ants in its collective behavior, it is observed
an evident emerging intelligence.
Utilizzo della stigmergia nell’informatica
The study of the behavior of ant colonies and their self-organizing abilities is
interesting for computer scientists because it provides distributed organization models that are useful to
solve problems of optimization and distributed control, emphasizing the role played by stigmergy
as a paradigm of distributed communication.
 https://it.wikipedia.org/wiki/Stigmergia , definition of stigmergy in nature