Drain Flies - School IPM - USU Extension

    Drain (Moth) Fly

    Psychoda phalaenoides

    Drain Fly

    Adult drain fly (Joseph Berger, Bugwood.org)

    Drain Fly

    Adult drain fly (Sanjay Acharya, Wikimedia Commons)



    • small: about 1/8 inch long
    • very hairy
    • wings covered in fine hairs; moth-like

    Nesting Habits

    • develop in the scum lining drains and sewer lines or decaying organic material
    • larvae hide behind scum making attempted treatments with boiling water, pesticides or other chemicals ineffective
    • can breed around broken pipes/drains beneath slabs or in crawlspaces, and enter buildings through floor cracks, etc.


    • drain scum
    • decaying organic matter


    • can spread disease through contact
    • bodies of dead flies may disintegrate to form allergens

    IPM Recommendations

    • Locate the breeding site and remove.
    • Remove larval habitat by using a hard bristle brush to remove the scum film from inside the drain.
    • Use an enzyme drain cleanser to maintain drains free of organic film.
    • If flies are coming from voids, crawl spaces or slabs, fix the moisture issue causing the problem and seal.

    Additional Resources

    IPM for Flies: Integrated Pest Management in Sensitive Environments (University of Nebraska-Lincoln Extension)