Moth flies - Psychodidae

At first I thought these were fruit flies but after some research I found that they are actually called Moth Flies or Drain Flies. I have had these in my house on occasion for years now. They are small flies with short hairy bodies and wings giving them a "furry" moth-like appearance. The adults have long furry antennae and the wings are shaped similar to that of the common Housefly. They typically come out at night and like dark damp places like sink drains.

Moth flies are easy to identify by the tiny hairs that make it look like a moth.  They are no more than 1/8 inch in length including the wings and are usually black in color.

Moth fly adults can be quite annoying in homes, appearing from sinks and bathtub drains.  These pests breed in remendous numbers in sewer plants and are easily blown towards homes by the wind.  Their small size enables them to penetrate ordinary fly screens.  There have been noted cases of bronchial asthma caused by inhaling the dust resulting from the disintegration of such small flies.

Moth flies lay eggs in a mass of 30 to 100.  These eggs hatch in less than 48 hours.  The larvae and pupae of the moth fly
live in the thin film found in drains, septic tank field lines or filter stones.  The larvae feed on sediment, decaying vegetation and microscopic plants and animals.

Moth fly larvae live in the moist film that develops on the sides of a drain and in the drain's trap.  The presence of many adult flies inside a drain is a good sign that the drain is a breeding site.  To check for possible breeding sites, place a length of tape across drains (or cracks in the floor) without totally covering the opening.  If the opening is totally covered, there will be no air flow and flies will not emerge.  Check the tape periodically.  If flies are found stuck to your tape, you have found a source. I have had them coming up from the floor drain in my laundry room and I have simply poured a bucked of hot water down the drain. Doing this regularly keeps the drain trap full of water and stops them from becoming a problem. It also stops the smell of the sewer gass from coming into my house.

These pests love the organic debris found in sewers, septic tanks, drains, wet brooms and mops, even the soil close to a leaking or ruptured plumbing line.  In homes, moth flies are generally found breeding in bathroom drains, particularly those in showers.