Finding a mysterious dirt tunnel climbing up your wall can be unsettling. One Reddit user recently posted images of a strange, growing structure inside their home—right above a clock on the wall. What started as a tiny patch quietly expanded over the course of just 18 days into a thick trail of soil. The internet chimed in with a clear and chilling answer: termite mud tubes.
Here’s why that matters—and what you should do next if you spot something similar.
Mud tubes are pencil-width tunnels made of soil, wood particles, and termite saliva. Subterranean termites, the most destructive termite species, build these tunnels as highways from their underground nests to your home’s wood framing. They rely on these tubes for protection from open air, which they cannot survive in for long.
These tubes are often seen on foundation walls, inside crawl spaces, or, as in this case, even high up on interior walls. The sight of them inside your home is a major red flag: it means termites are already inside your walls.