Termite mud tubes (also known as shelter tubes or mud tunnels) are iconic structures built by subterranean termites — constructed from a mixture of soil, termite saliva, and feces, forming pencil-thick (approximately 5–10mm wide) tunnels that extend along foundation walls, crawl space wood beams, or pipe surfaces.

The function of these mud tubes is to provide termites with a closed, moist, dark passageway — termites have soft bodies with extremely thin cuticles and will die from dehydration within minutes of exposure to open air.

Mud tubes enable termites to safely travel from the underground nest to wood food sources without being killed by dry air or exposed to predators (such as ants).

The discovery of mud tubes is definitive evidence of termite infestation.

Inspection method: Gently scrape open a small section of a mud tube with a screwdriver — if worker termites appear within minutes and begin repairing the damaged section, the tunnel is actively in use.

Common locations for mud tubes: interior and exterior foundation wall surfaces, where crawl space wood beams contact the foundation, along water and electrical conduits, and near moist areas in bathrooms and kitchens.