Why do ants fight each other?

Every ants goal in life is to ensure that its own colony lives as long and prosperous as possible; so that its genes are passed on to future generations. To make sure this happen they must fight off any competition that takes their supplies and space. Even within the same species, ants of different colonies will fight. Each colony has its own chemical smell so that all ants can determine who is a friend and who is a foe. There are a few exceptions to this, some species and colonies can coexist. The Argentine ant has colonies that have merged into the largest colonies ever recorded.