Subterranean termite nests consist of rooms (known as galleries) and tunnels. Termite tunnels often are called mud tubes, or shelter tubes, since they are made of soil and provide a protected walkway that connects the nest with above-ground food sources.
Termite shelter tubes can extend 60 feet or more and may be found along building walls reaching up to one or two stories above ground, especially where there is high humidity or a water source. Both native and Formosan subterranean termites have been found above the tenth floor in buildings. There is no limit to how high they can go up, if they find adequate moisture.
Subterranean termites also build tunnels inside their nests underground. These mud tubes connect the different rooms of the termite colony and allow termites to travel to food sources and move to rooms with optimal temperatures.
Both subterranean termites and termites that inhabit wood (such as drywood termites) create tunnels in the wood grain as they digest the cellulose. Damaged wood typically makes a hollow sound when tapped.
What Do Termite Tunnels Look Like?
Termite Tunnel in a Sub Floor:
As these pictures of termite tunnels show, mud tubes are earth-colored and typically about the width of a pencil, though they may range in diameter from 1/4 inch to 1 inch.
Termite Tunnel on Wood Beneath a Home: