Foraging worker termites, the ones that eat wood to
feed the rest of the colony, must stay in moist conditions and away from
natural enemies like ants. To get across barriers between the soil and the wood
above, termites construct small, meandering “mud” tubes from moist soil and
excrement. The tubes are about the diameter of a pencil, though they can become
wider. Tubes can be seen on foundation walls or inside walls, on plumbing pipes
and spanning crawl spaces between the ground and the subfloor. These termite
highways are a sure sign termites are or have been in the home.