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)