What do termites use to line their tunnels for moisture retention?

Termites utilize salivary secretions to line their tunnels primarily for moisture retention. Their saliva contains special proteins and substances that help maintain humidity levels within their tunnels, providing a stable environment suitable for their survival and the condition required for digesting cellulose from wood. This moisture-retentive characteristic is crucial because termites are sensitive to dry conditions, and the saliva helps to prevent the tunnels from collapsing and reduces evaporation, ensuring their habitat remains conducive for their activities.

In contrast, while wood particles, soil, and plant fibers can play a role in the overall structure and materials used in their nests or tunnels, they do not serve the specific moisture-retention function that salivary secretions do. Thus, salivary secretions are integral to how termites construct their living environments to optimize moisture retention.