When do hermit crabs shed their outer skin?

Hermit crabs shed their exoskeletons as they grow. As the crab grows, its exoskeleton becomes too tight and it must shed it in order to continue to grow. The process of shedding the exoskeleton is called molting. Molting is a complex process that can take several days. During molting, the crab will withdraw into its shell and its body will begin to break down the old exoskeleton. Once the old exoskeleton is broken down, the crab will shed it and its new exoskeleton will begin to harden. The new exoskeleton will be larger than the old one, allowing the crab to continue to grow.