Drain Fly

Drain Fly Identification

Drain flies are characterized by their fuzzy appearance and their shape. Fully matured drain fly adults are about 1.5 mm to 5 mm long and will range in colors from yellowish to brownish gray to even black. Drain flies possess antennae and wings that point apically, which means that they spread out at the bottom and meet at a point towards the head, giving them a triangular shape when they are at rest. The wings have veins that are vertically striped down the wings and are also hairy. The shape and the hair on their wings give drain flies the other common name, moth flies, because they are similar in physical appearance to moth insects.

Drain fly larvae is fairly large compared to a fully matured drain fly. Mature larvae is about 4mm to 10mm long and like most fly larvae, drain fly larvae is eyeless and legless. They are not quite cylindrical in form and their heads and terminal rear are both more narrow that their bodies. They are a pale cream color but their heads, terminal rears and their strap-like bands are all dark in color.

Drain Fly Behavior

The size of drain flies are so minute that it plays out well in their advantage but will cause extreme nuisance for a homeowner. They are able to fit through any ordinary screening. Drain flies are actually weak fliers and can only fly for very short distances. Inside, many people may see them flying around in short and very jerky movements. Most people will catch them crawling on the walls or on other surfaces. Drain flies are the most active during the evening time and during the day. They are often seen resting on surfaces that are close to drain openings or resting in shaded areas on the outside.

Usually, due to their short life span, only a few adult drain flies can be found in a home at one time and they are constantly replaced by new emerging adult drain flies. If you are noticing a large number of adult drain flies, this usually means that there is a sewage plant or a large area that acts as a type of sewage drain. Although drain flies cannot fly for long distances, their size allows them to be easily carried by the wind for up to 300 feet.

How to Get Rid of Drain Flies

To completely get rid of drain flies in the house requires thorough inspection. The breeding site must be located in order to eradicate a drain fly infestation. There are key places to check as sources of breeding sites. These places include but may not be limited to slimy drains, saucers under potted plants where water is collected, roof gutters, sewer leaks or sewer backups, dirty garbage cans and septic tanks. If there is a large infestation and the population of fully matured drain flies is concentrated, they may not be limited to areas around the home. Rather, a homeowner may want to check for a nearby sewage treatment plant. Although drain flies are not strong fliers, they can be carried by the wind for up to 300 feet. Therefore if a sewage treatment is nearby, it is possible for the adult drain flies to be carried to your home. Also, weed control should be maintained so that you can get rid of roosting sites.

Vertical surfaces and drains should be treated with a properly labeled pesticide. Drain gels will flood out possible breeding and nesting sites that are located directly within the drains. For surfaces, a liquid spray that has drain flies properly labeled will work. Microencapsulated and wettable powders formulations seem to be particularly effective against drain flies. Also, pyrethrin or pyrethroid based aerosols can be used to kill and control a large number of fully matured drain flies on contact.