moth, fly, or moth fly
Location: Washington State
February 3, 2011 2:23 pm
Found these larvae in my toilet bowl. I flushed and more appeared. I looked in the tank and found that the tank had been retrofitted with a plastic eco insert. In the main tank there was about 1/4” of stagnant water because the water was being diverted into the insert. I think that a fly or moth laid eggs in the stagnant water and then somehow the larvae moved into the plastic insert and with every flush some get sucked from the insert into the bowl. Because I don’t know how the retrofit works, I haven’t taken it apart to check.
We actually believe this is a pupa and not a larva, and your supposition that it might be a Moth Fly in the subfamily Psychodinae is probably correct, though your images look different from the stages of the Filter Fly, Clogmia albipunctata, that are pictured on BugGuide. Your individual is more elongated than the this image of a Filter Fly Pupa from BugGuide, however, there are other members of the subfamily that have a similar habitat. BugGuide also provides this information on the subfamily: “Larva: eyeless and legless; head darker and narrower than body; each segment with one or more dark rectangular bands dorsally; terminal segment narrows, forming dark-colored breathing tube Pupa: resembles minute grain of brown rice” and “Adults often found around sewage installations, in public washrooms, and bathrooms in homes, and are attracted to light; larvae live in organic sludge that forms on inner surfaces of drains and sewage pipes; pupae occur on the surface of the organic film that the larvae have been living in.” Finally, BugGuide has this information on the life cycle of Moth Flies: “In the home, females lay irregular masses of 30-200 eggs in the organic gelatinous film lining drains, particularly in bathtubs and showers; eggs hatch 32-48 hours after being laid, when ambient temperatures are 70ºF (about 20ºC), and larvae pupate 9-15 days later; pupa stage lasts 20-40 hours; development time from egg to adult is 7-28 days, depending on temperature and food availability; adults live for about two weeks.” Since the Moth Fly Pupa are on the surface, they are easily transferred from the eco insert to the tank and bowl during the flushing process. The appearance of Moth Flies in otherwise sanitary bathrooms might be due to poorly engineered, but well intentioned methods for water conservation. Thank you so much for sending your letter and excellent photographs.