|“|| 'Midgewater! There are more midges than water!'
'What do they live on when they can't get hobbit?' asked Sam, scratching his neck.
–The Fellowship of the Ring, A Knife in the Dark
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.
Midges will spawn more midges over time if the amount of nearby midges is below a certain limit, inevitably leading to a very densely midge-populated area. However, while midges may reproduce outside Midgewater and the Far Harad Jungle, the chance of this happening is much lower and the midge limit will be reached sooner.
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.
Animals of Middle-Earth