Termites are found in every state in the United States except Alaska, but are most common in the warm and humid southeast. $2.2 billon is spent annually for termite control in the United States mainly to control subterranean termites. Because termites consume cellulose, the main structural components of plant cells, any wood material in a house is a potential food source.  Most people become aware of an infestation when annual flights of winged termites (called alates) occur in structures. Termite species colonies contain three primary castes; the reproductives (king, queen, alates, alate nymphs, and supplementary reproductives), soldiers, and workers. A single colony of subterranean termites may contain 100,000 - 1,000,000 termites and forage up to 150 feet in search of food. When subterranean termites search for food aboveground, they may enter a house through small cracks or joints in the foundation, or by building shelter tubes along the foundation wall that connect the underground termite population with aboveground food sources.