Which hormone primarily controls molting in insects?

The hormone that primarily controls molting in insects is ecdysone. Ecdysone is a steroid hormone that triggers the process of ecdysis, which is the shedding of the old exoskeleton. This process is essential for insects as they grow, and it allows them to move into larger and often more advanced stages of development, such as from larva to pupa to adult.

Ecdysone acts on the insect's tissues to initiate the complex series of changes needed for molting, including the formation of a new cuticle and the breakdown of the old one. This hormone ensures that the insect can progress through its lifecycle stages effectively.

In contrast, insulin is involved in regulating metabolic processes, juvenile hormone plays a crucial role in determining the developmental stage of the insect and influences whether it will molt or develop into a more mature form, and thyroxine is not involved in insect development but is instead crucial for metabolism regulation in vertebrates. Understanding these roles clarifies why ecdysone is specifically essential for molting in insects.