Gnats are any of several species of small, non-biting flies. They appear suddenly, forming annoying swarms in the air as they mate. While they look like mosquitoes, these gnats cannot bite. Usually, they live for just a few days, and then disappear. Some are attracted to light and may be a nuisance, landing on people or entering homes or businesses.
The immature stages of gnats develop in standing water in pools, containers, ponds, clogged rain gutters, or in some cases, wet soil in seepage areas. Most feed on algae or decaying plant matter.