Drain Fly Facts & Information

What Orkin Does

Generally, the best control for these flies is to remove the breeding site, which is the organic material that collected in the drain. The site must be located and cleaned. Drain cleaner will not fix the situation. Read more about drain flies and bleach.

Once the material is removed (along with the larvae) the problem is solved, except for the adult flies. They will live about 20 days, but will have no place to lay eggs to continue their life cycles.

Your local Orkin Pro is trained to help manage drain flies and similar pests. Since every building or home is different, your Orkin Pro will design a unique fly treatment program for your situation.

Appearance

• Appendages: These flies have six legs and a pair of wings and antennae.

• Body: Light gray or tan body and lighter-colored wings. The body and the wings are covered with long hairs, giving the fly a fuzzy appearance.

• Characteristics: When at rest, the drain fly folds its wings over the body in a characteristic roof-like manner.

• Size: Drain flies measure about 1.5 to 5 mm long.

• Larvae: Drain fly larvae are not longer than 4 to 10 mm when fully mature and they are slender with a dark strip on the "back" or dorsal area. Larvae do not have eyes, and they are legless. On one end of the larva, there is a dark breathing tube used to extend out of the film to obtain air.

Habitat

Drain flies are common in moist areas coated with nutrient-laden organic material. As their name implies, they are found in house and storm drains. They can also be found near decaying logs and compost piles.

Diet

Drain flies feed on organic matter and sewage.

Life Cycle

Eggs are laid in irregular masses almost anywhere decomposing organic materials are found. Drain fly eggs hatch into white, nearly translucent larvae. These larvae have been known to survive dramatic temperature swings and low oxygen levels. Under favorable conditions, the flies can go through one generation in as little as one week. Two to three weeks is more typical.

Larvae

Usually, the homeowner never sees drain fly larvae since the larvae are located in the gelatinous film inside drains. However, sometimes, when drains are taken apart, larvae can be found in the film. In small numbers, larvae are considered beneficial because they break down materials that cause drain clogs. They have extremely strong jaws and are capable of cutting through layers of dense slime and build-up.

Drain fly larvae are not longer than 4 to 10 mm when fully mature and they are slender with a dark strip on the "back" or dorsal area. Larvae do not have eyes, and they are legless. On one end of the larva, there is a dark breathing tube used to extend out of the film to obtain air.

Adults

After the larvae mature, they will pupate or rest until they emergence as adults. The adult is the only life stage usually observed. Adult drain flies usually live about two weeks, but newly emerged adults rapidly replace them. These flies are also known as moth flies due to their appearance: they are small and furry with large, ovoid wings and prominent antennae. When at rest, the drain fly folds its wings over the body in a characteristic roof-like manner.