• Moth Fly Flies

    Moth Fly
  • Moth Fly


The main way of eliminating these insects is to find their source. Removing the organic matter in which they develop usually solves the problem. Cleaning with a product especially designed for the purpose and thoroughly brushing the pipe walls is usually sufficient. Remember to clean the overflows in bathroom sinks and baths. If there is a large population of adult flies, a quick spray with Maheu&Maheu Maheu&Maheu Flying Insect Killer will normally eliminate them.


  • Clean and brush drains, pipes, and overflow outlets
  • Spot spray with pyrethrin-based-based insecticide in places with a lot of flies


  • Take care of drains to prevent surface buildup of organic matter
  • Repair and dry up after water leaks quickly

Description and development

The moth fly is a holometabolous insect (having four very different life stages) in the Psychodidae family of the Diptera order. It is a very small fly, generally 1 mm to 5 mm long. It is covered in silvery-gray hairs, giving it the appearance of a small moth. Its wings are quite broad and oblong, which prevents it from flying long distances.
Moth flies lay their eggs in clumps of 30 to 100 eggs. The eggs hatch within 48 hours. The larvae and pupae develop in organic matter, such as silt clinging to the walls of water pipes and drains. The larvae take between 9 and 15 days to develop, but the pupal stage lasts only 20 to 40 hours. The emerging adult is sexually mature and can reproduce.


If moth flies develop indoors, it is generally due to silty drains. Silt often builds up drains (in basement floors, sinks, baths, and showers, etc.) that are rarely used. The adults can be seen flying nearby, and their presence may signal a damaged pipe or sewer backup.

For more information on Moth Fly, please read issue 23 of our technical newsletter The Gatekeeper.

Go to top