How do waxy layers in the exoskeleton help land arthropods avoid drying out?

For land-dwelling arthropods, preventing desiccation is a critical survival challenge due to their small size, which makes them highly susceptible to evaporative water loss. To address this, these animals have evolved a specialized exoskeleton that serves as a protective barrier.12

The outermost layer of this exoskeleton, known as the epicuticle, contains waxy compounds that act as a waterproof covering. By secreting this layer of wax onto the surface of the cuticle, arthropods significantly reduce the amount of water lost through evaporation. Because this waxy layer is fragile, it is often protected by a thin, cementlike substance secreted by dermal glands.12

In addition to preventing drying out, these waxes serve as a water repellent, which helps protect the animals from being submerged by rain or dew. Arthropods that lack this waxy epicuticle, such as pill bugs, typically inhabit moist environments like leaf mold or soil to avoid the danger of desiccation.2