The workers form by far the largest caste and live exclusively underground; they are pale, have large toughened heads, and lack eyes. When the first workers are old enough to leave the nest, they begin to undertake their multiple duties. First, they search for food, leaving the queen free to devote all of her time to egg-laying. Eventually, the workers provide food for the king, queen, larvae, and soldiers. Dead wood is the main part of a worker termite's diet. Often, workers eat wood before returning to the colony with it. In such cases, they partially digest it and transform it into a milky liquid. When they reach the colony, the workers feed the other termites through regurgitation; this form of food is called stomodeal food.
Most species of termite eat wood, but their digestive enzymes are not able to break down the nutritious part of the wood, called cellulose. To do this, termites have the help of microorganisms residing in their bodies that break down the cellulose into a substance that they can digest.
The workers also take part in building the colony. In the majority of species, the workers dig underground systems of tunnels. They create complex structures, which protect the inhabitants from their enemies. Because some nests contain as many as three million termites, the nests need the right level of oxygen and carbon dioxide for the members to survive. Therefore, workers build nests with ventilation systems regulating the colony's environment. It is thought that intestinal gases, including methane, rise to the top of the nest and diffuse through the walls and out of venting shafts.
Another task that the workers must carry out is caring for the colony's young. When the queen lays her second series of eggs—about one month after her initial laying—the workers take the larvae into the brooding chamber where they care for them. As part of their care, the workers turn over the eggs periodically and check them for signs of parasite damage.