Subterranean Termites:

Subterranean termites live in colonies underground, and nest in the soil to obtain moisture, or in wood that is often wet.  They easily attack any wood in contact with the ground.  If the wood does not contact the soil, they can build mud tunnels or tubes to reach several feet above the ground.  These tunnels can extend for 50-60 feet to reach wood and often enter a structure through expansion joints in concrete slabs or where utilities enter the house.

Subterranean termite feeding follows the grain of the wood.  Unlike drywood termites, subterranean termites do not push wood particles or pellets (fecal matter) to the outside, but rather use it in the construction of their shelter tubes.

Subterranean termites feed on wood or other items that contain cellulose, such as paper, fiberboard, and some fabrics derived from cotton or plant fibers.