Worse, there are instances when termites are present but cannot be seen because the areas are inaccessable or simply obstructed from view. Consequently, every inch of the building that comes in contact with the soil must be checked if at all possible. Concrete and masonry walls and floors must be examined for cracks or gaps through which termites could enter. The entire structure must be inspected for indications of hollowed out, weakened wood, and especially for signs of mud tubes through which they can reach wooden structural members. Mud tubes on masonry walls or on support piers are evidence of an infestation.
Wood damaged by termites has galleries that tend to run with the grain.
The galleries formed by subterranean termites can be distinguished from damage by other wood destroying insects because often they contain particles of soil rather than saw dust. The workers leave the colony to forage, but must return to the soil at least every 24 hours for moisture. Sites where wood floors, beams studs, or joists are in close contact with damp soil, such as under dirt filled porches, or in crawl spaces, provide easy access between the colony site and their food supply. Further, where there are water leaks in the building, such as leaking pipes, the constant damp wood may enable secondary colonies to be formed in the building itself. The subterranean termite's need for constant moisture is a characteristic that can aid in the control of these insects.