Why does an arthropod exoskeleton limit the maximum size of animals living on land?

The exoskeleton of an arthropod limits its maximum size on land primarily due to the mechanical and physiological constraints of its structure and the process of molting.12

On land, an arthropod lacks the buoyancy provided by water, which supports the bodies of large aquatic species like spider crabs. To support a large body mass on land, an arthropod would require an excessively thick and heavy exoskeleton, which would become inefficient for movement.23

Furthermore, the necessity of molting—the periodic shedding of the rigid exoskeleton to allow for growth—creates a critical vulnerability for larger animals. Following a molt, the new, soft exoskeleton is initially flexible and lacks the structural integrity to support a large body, which could lead to the animal's collapse under its own weight. Additionally, the process of extracting the body from the old shell and the period of time required for the new skeleton to harden leave the animal defenseless and physically fragile, making significant size increases biologically impractical for terrestrial species.1425