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How does an insect form a new cuticle during molting?

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Illustration showing a variety of adult insects, each labeled with its common name and order, including walkingstick, earwig, stonefly, tree cricket, dragonfly, female scale, cat flea, thrips, sucking louse, thysanuran, ant, scarab beetle, stinkbug, mosquito, and cabbage butterfly, highlighting their diverse shapes and sizes. — insect An illustration of insect diversity.

An insect forms a new cuticle through a highly regulated process that occurs during the molting cycle, specifically during the pharate stage while the old exoskeleton is still in place.12

The process begins with apolysis, where the old cuticle separates from the underlying epidermis. Once separated, the epidermal cells secrete a new epicuticle, starting with the cuticulin layer, which protects the cells from the enzymes in the molting fluid.12

Following the formation of the new epicuticle, the insect secretes a new exocuticle and subsequently a new endocuticle. Much of the material required to construct these new layers is recycled from the old cuticle, which is broken down by enzymes like chitinase and peptidases found in the molting fluid.1

After the old cuticle is shed during ecdysis, the new, soft cuticle undergoes sclerotization. During this phase, quinones form cross-links with proteins and chitin, hardening and stabilizing the new structure.23