4954 N. Shamrock Place, Tucson, AZ 85705

Drain Fly

Psychoda alternata

Drain Fly

Physical Features

1/5 to 1/6 inch long, tan-colored body, black and white wings. Body and wings are covered with hair. The wings appear larger than their bodies and are blamed for their weak flying ability. Antennae have 13 segments with the last being a bulb-like shape.

Life Cycle

Complete metamorphosis
Eggs are laid in masses numbering 10-200 on the gel-like film that covers filters, drains, pipes or sewage disposal beds. Larvae emerges 32 to 48 hours later. They are gray, legless, 3/8 inch long, and live in the film breathing through a tube. This continues for 9 to 15 days then pupae float to the surface. Adults emerge after 20 to 40 hours. Adults live about 14 days.


  • Diet: Adults feed on flower nectar and polluted water
  • Activity: Most active during the evenings
  • Preferred Climate: 70-90 degree temperatures
  • Defense: Small size helps evade harm.
  • Cautions: Do not bite humans. Nuisance and possibly spread disease.
  • Home Invasion: Will be found clinging to bathroom, kitchen or basement walls. More specifically found on sides of showers and tubs or hovering over drains.

Helpful Hints

  • Eliminating stagnant water accumulated near or in the home.
  • Thorough sanitation practices.
  • Recommend regular pest control service plan.
  • Remove the breeding site.

Interesting Facts

They are possibly the most common insects living in sewage plants.



Nesting Sites

Occasional problems in homes, usually emerging from sink drains especially in the spring.