Chitinous exoskeleton is one of the keys to the success of arthropods on land because
It must be occasionally moulted (shed) to facilitate growth
It enhances respiration through the body surface
It is impermeable to water and prevents desiccation
It helps in absorption of moisture
Chitinous exoskeleton is impermeable to water and prevents desiccation. This is one of the keys to the success of arthropods on land.