SI is the property of a system whereby the collective behaviors of agents interacting locally with their environment cause coherent functional global patterns to emerge. SI provides a basis with which it is possible to explore distributed problem solving without centralized control or the provision of a global model. One of the cores tenets of SI work is that often a decentralized, bottom-up approach to controlling a system is much more effective than traditional, centralized approach. Groups performing tasks effectively by using only a small set of rules for individual behaviour is called swarm intelligence. Swarm Intelligence is a property of systems of non-intelligent agents exhibiting collectively intelligent behaviour. In Swarm Intelligence, two individuals interact indirectly when one of them modifies the environment and the other responds to the new environment at a later time. For years scientists have been studying about insects like ants, bees, termites etc. The most amazing thing about social insect colonies is that there’s no individual in charge. For example consider the case of ants. But the way social insects form highways and other amazing structures such as bridges, chains, nests and can perform complex tasks is very different: they self-organize through direct and indirect interactions. Swarm describes behavior of an aggregate of animals of similar size and body orientation, often moving en masse or migrating in the same direction. Swarming is a general term that can be applied to any animal that swarms. The term is applied particularly to insects, but can also be applied to birds, fish, various microorganisms such as bacteria, and people. The term flocking is usually used to refer to swarming behavior in birds, while the terms shoaling or schooling are used to refer to swarming behavior in fish. The swarm size is a major parameter of a swarm.