Besides wood, what do subterranean termites need to survive?

Subterranean termites require moisture in addition to wood for their survival and activity. These termites thrive in environments with adequate humidity and moisture, which facilitates their feeding and nesting behaviors. Moisture is crucial for their physiological functions, allowing them to maintain their bodies' hydration and aiding in the digestion of cellulose found in wood.

While air is also necessary for their survival, it is abundant in most environments where termites are found and does not specifically highlight a critical requirement for their ecology. Soil is important for subterranean termites as it provides a habitat and protection; however, moisture is the vital element they actively seek to maintain their colony’s health. Sunlight, on the other hand, is detrimental to subterranean termites, as they thrive in dark, moist conditions derived from their underground tunnels and extensive networks. Therefore, moisture stands out as the essential second requirement for their existence, making it the correct choice in this context.