2. Molting of the insect cuticle

Recent questions

• What is the molting process in insects?

  The molting process in insects, also known as ecdysis, is a critical biological event that allows insects to grow by shedding their old exoskeleton. This process is initiated by the insect molting hormone, 20-hydroxyecdysone, which triggers epidermal cells to activate specific genes responsible for the formation of a new cuticle. As a result, the cells undergo mitosis or enlargement, leading to a separation of the old cuticle from the epidermal layer, a phase known as apolysis. During this stage, a gel-like substance fills the space between the old cuticle and the epidermis, containing inactive enzymes that will later digest the old cuticle, allowing the insect to recycle up to 90% of its chitin and protein for the new exoskeleton.

• How do insects shed their skin?

  Insects shed their skin through a process called ecdysis, which is the final step of the molting cycle. After the initial preparation involving the activation of molting hormones and the formation of a new cuticle, the actual shedding occurs when the old exocuticle and epicuticle are released as exuvium. This process is triggered by the hormone bursicon, which plays a crucial role in the sclerotization of the new procuticle. Sclerotization involves hardening the new cuticle using polyphenols, ensuring that the new exoskeleton is robust and ready for the insect's growth. Once the old skin is shed, the insect will not undergo any further changes until the next molting cycle begins, during which new layers of cuticle are continuously deposited.

• What role does 20-hydroxyecdysone play?

  20-hydroxyecdysone is a pivotal hormone in the molting process of insects, acting as the primary trigger for the initiation of ecdysis. This hormone stimulates the epidermal cells to activate genes that are essential for the molting process and the formation of a new cuticle. When 20-hydroxyecdysone is released, it prompts the cells to either undergo mitosis or enlarge, leading to the separation of the old cuticle from the epidermis, a phase known as apolysis. This hormone is crucial for ensuring that the insect can grow by facilitating the recycling of materials from the old cuticle, which is vital for the formation of the new exoskeleton.

• What happens during sclerotization?

  Sclerotization is a critical phase that occurs after the shedding of the old exoskeleton during the molting process in insects. This process involves the hardening of the newly formed procuticle, which is essential for providing structural integrity to the insect's new exoskeleton. Triggered by the hormone bursicon, sclerotization utilizes polyphenols to strengthen the new cuticle, transforming it into the new exocuticle. This hardening process ensures that the insect is protected and can function effectively in its environment. Once sclerotization is complete, the new exoskeleton is fully formed, and the insect will not undergo any further changes until the next molting cycle begins.

• Why do insects recycle old cuticle materials?

  Insects recycle old cuticle materials during the molting process to maximize resource efficiency and support their growth. When an insect molts, a significant portion of the old cuticle, which is primarily composed of chitin and proteins, is digested by enzymes that are activated in the ecdysial space. This recycling allows the insect to reuse up to 90% of the chitin and protein from the old exoskeleton in the formation of the new procuticle. By reusing these materials, insects can conserve energy and resources, which is particularly important given the energy-intensive nature of the molting process. This efficient recycling mechanism is a key adaptation that supports the growth and survival of insects throughout their life cycle.