Today we will discuss a photograph that one of our readers sent us. She asked, “What is this?! Did it come out of the dog or come into the house on its own. Help!” The photograph shows a brown worm with a thin, black line running down its side. The worm has a shiny appearance and we think it is probably a few inches long, though the size is just a guess because there isn’t any object in the photograph that we can scale it against.

We have written several articles about worms that look a lot like this creature. We think it might be a terrestrial flatworm, or a land planarian. Despite their name, not all of these worms are truly flat, which would attribute to the rounder shape of this worm. A handful of land planarians have dull coloring, like this one, which helps them blend in with their environment. Many more are brightly colored and distinctively patterned. The earth-toned ones are sometimes confused with leeches and/or slugs because of their similar coloring and slimy appearance. Land planarians range a lot in potential size. Some can grow to be a meter long, while others are mere millimeters.

We aren’t sure how this worm wound up in our reader’s home. Since flatworms prefer leaf litter or moist soil, a hardwood floor or plush carpeting doesn’t exactly appeal to their taste. If we had to guess, we would say the specimen probably crawled in through an open door or window, or was accidentally dragged in on a shoe. Of course, it also could have come from the dog as our reader suggested. It might have been attached to its fur, or it could have been excreted from it. We don’t think this is a parasitic worm, but if our reader is worried about her dog’s health, we recommend she take it to the vet. Land planarians aren’t harmful to humans,so our reader shouldn’t worry about this specimen too much in terms of her own health, but we don’t know whether they might impact the health of other animals.

In conclusion, one of our readers discovered a brown worm in her home. Based on the photograph she included, we think this organism might be a terrestrial flatworm.