Which of these organisms relies on a moist terrestrial habitat?

The pillbug, also known as an isopod, is significantly reliant on a moist terrestrial habitat for its survival. This organism is adapted to life on land but requires high humidity levels to prevent desiccation, as it has a soft exoskeleton that can easily lose moisture. Pillbugs tend to inhabit environments such as leaf litter, soil, and decaying wood, where they can find the moisture necessary for their physiological needs. They are commonly found in gardens and forested areas that provide the humidity they need to thrive.

In contrast, spider mites can tolerate drier conditions, and many species thrive in various habitats including dry and arid environments. Wasps, depending on the species, can be found in diverse habitats but are not particularly dependent on moist environments. Fleas, while often found on animals and in their environments, do not specifically rely on moist habitats for their life cycle; rather, they can adapt to a range of conditions. Thus, the pillbug is the best example of an organism that specifically relies on a moist terrestrial habitat.