Drain Flies

Psychodidae

Drain flies are a common household insect that is frequently confused with fruit flies and fungus gnats. You may also know them by other names, like sink flies, filter flies, sewer flies, or sewer gnats. Typically found near sinks, bathtubs, and showers, these insects multiply easily and can become a fast nuisance in your home.

Drain Flies
Color Light gray or tan body and lighter-colored wings.
Legs 6
Shape Short, hairy bodies and wings give them a "furry" moth-like appearance
Size 2–3 mm
Antennae True

What Causes Drain Flies?

Drain flies thrive in stagnant and standing water. Common sources include slow or clogged drains, rarely used and unused toilets, refrigerator drain pans, and standing water created by leaking pipes. They typically enter buildings through basements, windows, and drains.

How Long Do Drain Flies Live?

Adult drain flies live for about 20 days, during which they will breed only once, often within hours of emerging from their pupal casings. Females will lay their eggs (between 30 and 100) just above the water line inside moist drains. Within 48 hours these eggs hatch into the larval form of drain worms. The larval stage lasts between 9 and 15 days, depending on species, temperature, and environment. The pupal stage lasts only between 20 and 40 hours. 

Are Drain Flies Dangerous?

Drain flies aren’t known to carry or transmit any human diseases, but infestations have been known to trigger asthmatic reactions. These small insects are opportunistic agents of myiasis (a disease that occurs when the body is infected by a parasite, namely fly larvae that need a host to develop).

How to Get Rid of Drain Flies?

The best way to get rid of drain flies is to eliminate potential breeding sites. The breeding site must be located and thoroughly cleaned. Look for potential breeding spots near drains or other sources of standing water. 

If you’re unsure which drain is the source, line a clear plastic cup with a very light coating of vegetable oil or petroleum jelly and invert over the suspected drain for several days. This will help catch emerging adults and identify breeding sites. Pouring hot water down the drain may provide short-term control, but never pour insecticides or drain cleaner down drains to kill drain flies. Get help from the professionals at Arrow Exterminators using the form below for persistent drain fly infestations.

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