This is what causes the damage to wooden structural members. Workers then go back down to the colony and feed the others. Tubes are sometimes built on the outside of walls to bypass an area, such as a brick or concrete wall. Subterranean termites need moisture at least in the form of increased humidity. Sometimes they will bring mud up from the ground and pack it in the damaged wood to provide the moisture.
Termites can travel hundreds of feet in search of wood food source.
They are slow but persistent. Two signs of termite presence that the homeowner is most likely to find are swarms of winged reproductives or mud tubes on the side of the foundation. The presence of the winged reproductives indicates an active colony 4 - 10 years old somewhere nearby. The colony may be in the house or in some wood outside. Mud tubes on the foundation, if they contain live termites, would indicate and active colony attacking the building.