We are assuming that you mean termites when you refer to wood bugs. Subterranean termites live in the soil -- not in the wood. They leave their colony looking for food (wood). If wood is a direct contact with the soil, the termites easily enter the wood and can do a considerable amount damage. If the wood structure is elevated above the ground by a concrete foundation, the termites will build mud tunnels called shelter tubes, to get from the earth to the wood. Left unchecked, termites can do thousands of dollars worth of damage. Treatment involves breaking wood soil contact, and chemically treating the soil to create a barrier between the termites and structure.