Imagine you’ve just returned home from a week long vacation only to find 22 worm-like creatures sluggishly swimming about at the bottom of your toilet bowl. You then recall that you gave some of your friends permission to stay at your house while you were away. Then a theory takes form in your mind that says one of your friends must have intestinal worms. You decide to call a professional entomologists at the local extension office with the hope that he/she can identify the alien creatures. After describing the situation, you email a picture of the worms to the extension employee, and in less than a minute, he responds with good and bad news. The good news is that none of your friends have parasitic worms, but the bad news is that you have a drain fly infestation, as the “worms” are actually insect larvae.

Believe it or not, this particular scenario is surprisingly common all over the world, and the above incident occurred in the northeast US. Not long ago, another woman noticed several worms in her seemingly clean toilet, but they eventually disappeared with a few flushes. However, each time the woman cleaned her toilet with bleach, the worms returned. In frustration, the woman described her situation on Facebook, and included pictures of the pests, hoping that someone could identify them. Not only were they identified as drain fly larvae, but dozens of people all over the world described having experienced the same situation in their bathroom.

In the natural environment, drain fly larvae develop within polluted water, sewage, excessively moist soil and other wet conditions where they are able to feed on a variety of microbe-rich forms of decaying organic matter. The appearance of drain fly larvae in toilet bowls indicates that waste is building up in a toilet drain, as drain fly larvae feed on hair and foul sludge that accumulates on the interior surface of sewage pipes. It is far more common for residents to experience issues with airborne adult drain flies than their larvae, but as it happens, reports state that finding drain fly larvae in toilets is most common in northern areas where drain flies inhabit sewers in large numbers in order to stay warm. Drain fly adults do not spread disease or bite, but they often emerge from drains in large numbers in kitchens, bathrooms and basements where the pipes lead to sewer systems. Since drain flies are poor flyers, they do not travel far from the drains in which they emerge, and the best way to prevent issues with these pests is to remove the grimy buildup within drains, and in many cases, professionals must remove sludge mechanically.

Have you ever found insects within your toilet bowl?