How long can the fifth instar of a subterranean termite last?

The fifth instar stage of a subterranean termite can last up to 2 years, making this the correct choice. This developmental stage is critical because it represents a significant phase in the life cycle of subterranean termites, where they mature and prepare to reach adulthood, ultimately impacting their ability to reproduce and contribute to colony growth.

Subterranean termites undergo several molts as they develop from nymph to adult, with the fifth instar being one of the last stages before reaching maturity. The duration varies based on environmental conditions and the availability of food resources, but the prolonged development time of up to 2 years reflects the complex nature of their life cycle and adaptation strategies that allow them to thrive in their habitats.

The other durations provided in the options do not accurately capture the lifespan of the fifth instar stage; while some earlier instars may last shorter periods, the transition to adulthood from the fifth instar can indeed take a considerable time, especially under favorable conditions.