The molting cycle in crustacean is controlled by hormones. Below is a snippet from a study on crustacean molting that explains the role of hormones in the molting cycle. Land hermit crabs continue to molt their entire life unlike some other crustaceans.

ERNEST S . CHANGM, ARILYN J. BRUCEA, ND

Coenobita cavipes Surface Molt
Coenobita cavipes Surface Molt

SHERRY L. TAMONE
Bodega Marine Laboratory, University of California, P.O. Box 247, Bodega Bay, California 94923

SYNOPSIS
In order to increase in size, arthropods must first molt (shed) their confining exoskeleton. This molting process is under the immediate control of the steroid molting hormone 20-hydroxyecdysone (20-HE).

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More articles on molting:
What is molting
Is my hermit crab dead or molting?