Midges spawn in swarms in the Midgewater biome and, less commonly, in the Far Harad Jungle. They are very annoying, but harmless, and can be killed in a couple of swats. Part of their annoyance is due to the fact that they are attracted to nearby players, buzzing above the player's head and following them relentlessly. They are also very noisy. There is also an achievement for shooting down a swarm of midges with a hired unit, called "Anti-Air Support". This can be done by damaging the midge swarm once to attract your ranged units to it.