The monolithic approach to robotics, based on the concept that one single unit is able to perform all the required tasks, is questionable when the required capabilities exceed those of one single individual unit. A swarm of robots, an assembly of independent, heterogeneous robots, is a potential answer to this problem mainly when adaptation to unpredictable situations is the critical issue. The software controlling a robotic swarm does not specify any central control unit, and operates purely on the basis of local information. These control strategies are usually inspired by insect behaviour, and are evolved by using generic algorithms and other evolutionary robotic techniques.