Subterranean termites represent the most widespread and destructive insect threat to wooden structures across North America. These insects consume wood, which is the foundation of their entire diet. Wood is sought because it contains cellulose, a complex organic polymer that serves as the colony’s primary source of nutrition. Subterranean termites are natural decomposers, and their ability to break down cellulose is what makes them highly damaging to human-built environments.
The Biological Mechanism of Wood Digestion
Termites are unable to produce the necessary enzymes to break down the complex cellulose found in wood. Their survival hinges on a mutualistic relationship with specialized microorganisms, mainly flagellate protozoa, that reside within their hindgut. These single-celled organisms secrete cellulase, an enzyme that hydrolyzes the cellulose into simple sugars, which are then absorbed by the termite host for energy.
The protozoa further ferment these sugars, producing acetic acid and other short-chain fatty acids that the termite can metabolize. Termite workers forage and consume the wood, but they also perform trophallaxis, or mouth-to-mouth feeding, to distribute the digested nutrients throughout the colony. This ensures that all members, including soldiers, reproductives, and developing nymphs, receive the necessary sustenance.
Beyond Lumber: Other Cellulose Sources They Consume
While structural lumber is the most concerning target for homeowners, the diet of subterranean termites extends to any material containing cellulose. This includes common household items like cardboard, paper products, and books. Termites will also consume the paper backing on drywall and particleboard as they tunnel toward more substantial wood sources.
Plant-derived textiles, such as cotton fabrics, can also be consumed because they are rich in cellulose. Termites are highly dependent on damp conditions to survive, so the availability of moisture often dictates their preference for a food source. Water-damaged wood or materials stored in damp basements or crawl spaces are often attacked first.
Identifying Evidence of Termite Activity
Foraging subterranean termites must maintain a connection to the soil for moisture and protection, so they construct unique earthen passageways called mud tubes. These pencil-sized tubes, made of soil, wood particles, and saliva, serve as protective runways across non-edible surfaces like concrete foundations or metal. Finding these tubes along foundations or basement walls is a strong indicator of active termite presence.
Another sign is damaged wood, which often sounds hollow when tapped because termites consume the wood from the inside out. They selectively eat the softer spring-growth wood, creating tunnels that follow the grain while leaving a thin, intact outer shell.
The most overt signs of a mature colony occur during the reproductive phase, involving the emergence of winged termites called swarmers. Swarmers leave the colony to establish new ones. A major indicator of an infestation is finding piles of their small, discarded wings near windowsills or light fixtures after a swarming event.