Gnat infestations in the home are typically caused by fungus gnats. These gnats are attracted to moist conditions with organic material. Over-watered house plants, places of condensation and rotting vegetation are the common culprits in gnat infestations.
Fungus gnats are very tiny and resemble mosquitoes, but unlike mosquitoes they do not bite and have no other capacity to harm anyone. However, their life cycle from egg to adult is extremely fast, usually less than two weeks. This means that an infestation of gnats can grow quickly and become a nuisance. Gnats get into homes in two primary ways. The first is through open doors or windows and the second is through eggs hidden in houseplants. Over-watering the house plants gives the gnat eggs perfect condition to hatch and grow. Adult gnats can also come in through doors and windows in warmer months and then find organic matter in which to lay their eggs. It is common to find gnats gathering around fruit or vegetables sitting out. They lay their eggs in these items and as they rot, the eggs turn into more flies and the cycle repeats.
Getting rid of fungus gnats is usually a matter of taking away their habitat. Another method is to lay out sticky traps for the adult flies.