Drain flies, also known as moth flies or sewer flies, are a common household insect often found near sinks, showers, and other damp areas. These small, fuzzy insects can quickly become a nuisance, prompting many people to wonder about their presence and potential harm.
Do Drain Flies Bite?
Drain flies do not bite humans or animals. Their mouthparts are not designed for piercing skin; instead, they are adapted for feeding on decaying organic matter and liquids found in their breeding environments. Any perceived “bites” are likely due to other insects, skin irritations, or simply the presence of the flies being a general annoyance.
Their soft, spongy mouthparts are suitable for lapping up liquids and feeding on bacterial and fungal films in drains and other moist, decaying organic material. This means they lack the ability to break human skin, unlike mosquitoes or biting flies. While not a direct health threat for biting, their presence can indicate unsanitary conditions.
Identifying Drain Flies and Their Habits
Drain flies are small, measuring about 1/8 of an inch long, with a distinctive fuzzy appearance due to hairs. Their wings are relatively large for their body size and are often held in a roof-like manner over their body when at rest, giving them a moth-like look. They are brown-gray or black. These insects are weak fliers, often seen resting on walls or ceilings and making short, hopping flights when disturbed.
These flies thrive in environments with stagnant water and decaying organic matter, which provides food for their larvae. Common breeding sites include the gelatinous film or slime that builds up in drains, pipes, and traps in kitchens and bathrooms. Other potential breeding locations include:
- Dirty trash cans
- Saucers under potted plants
- Condensate pans of refrigerators or air conditioners
- Septic tanks
- Moist compost piles
The life cycle from egg to adult can be completed in about 21 to 27 days, with eggs hatching within two days and larvae developing for 9 to 15 days in the organic sludge.
Controlling Drain Fly Populations
Controlling drain fly populations focuses on eliminating their breeding sites, which are the moist, organic film where their larvae develop. Thoroughly cleaning drains is the primary method to address an infestation. This involves physically removing the organic sludge and slime from inside pipes. Using a stiff, long-handled drain brush can help scrub away this buildup.
After mechanical cleaning, flushing drains with hot water can help dislodge any remaining material. A mixture of baking soda followed by vinegar can also assist in breaking down organic matter in drains. For persistent issues, specialized microbial drain cleaners, which contain bacteria that consume organic waste, can be effective as they work along the entire pipe system. Beyond drains, it is important to inspect and clean other potential breeding grounds like leaky pipes, clogged gutters, or any areas where standing water and organic debris accumulate.