Fungus gnats tend to fly all around lights and fixtures throughout the house. They are often mistaken for fruit flies and can be very annoying. Control can be difficult.
Fungus gnats are one of the small flies 4-5mm long. Their body is longer than a fruit fly shaped more like a small mosquito. Due to their short life cycle they are very prolific. As their name implies the larvae of the fungus gnats feeds on fungi, decayed vegetable matter and damp soil. In homes they may be found in the soil of house plants in particular ferns. Often found outdoors in decaying leaves or other matter, the adults may enter through the window and door screens when attracted by lights.

• If you have live indoor plants check the soil of all of them to see if it is wet, old or has mulch. These plants may be far removed from where you see the adult flies.
• Change the soil of all potted plants unless you know it is fresh and not over watered.
• Do not water the plants until they require moisture.
• Outdoors remove all accumulated debris from around the house.
• Pesticide treatments are not very effective but may be used to reduce the adult activity.
• Sanitation and removal of breeding material is the best and only real solution.