One of our readers found a black worm-like-organism in her toilet bowl after urinating. Like any bug-fearing human, her initial thought was that she must be dying from an internal worm infestation. However, after calming down and doing more research she thinks it might be a drain fly larva, not some deathly parasite. She described the specimen as: black, 1/2 inch long, segmented-ish, with a small head, and maybe a tiny split at the tail. She says is swam/crawled up the toilet bowl. What kind of creature is this?

We agree with our reader, we think the creature might be a drain fly larva. Drain fly larvae are commonly found in toilets, and they roughly match the appearance of the specimen in the photograph. While drain fly larvae aren’t segmented, they can appear that way. Here is an example of a drain fly larva photographed under a microscope from another reader:

As you can see, the texture and pattern of the body makes it look “segmented-ish.”

We are hesitant to confirm that she definitely found a drain fly larva for two reasons: the color and the size. First, drain fly larvae are often translucent with a black head. The specimen our reader found is very dark black, or at least appears that way in the photo. Of course, not all drain fly larvae look the same, and it is totally possible that this one is simply darker. Second, drain fly larvae are typically really small. At their largest, they are 10 mm long, which is only about .4 inches. However, the average size is about half of that, around .2 inches. So, either our reader found an especially large drain fly larvae, which is possible, or the creature isn’t a drain fly larva.

If this is a drain fly larva, our reader just needs to clean out her toilet. Drain fly larvae feed on the organic matter lines the pipes leading up to a toilet bowl. So physically removing the grime with a brush and cleaning gel will get rid of any other drain fly larvae feeding in her toilet. If the creature isn’t a drain fly larva, cleaning the toilet can’t hurt. As long as she doesn’t continue to find these creatures in her toilet, or in other places around her home, she shouldn’t stress about the situation.

In conclusion, one of our readers found a specimen in her toilet bowl. We aren’t 100% convinced that it is a drain fly larva, but we think it is a good match!