Hormonal Control of Moulting

diagram illustrating interaction between hormones and moulting

When an immature insect has reached the point in its development where it needs a larger exoskeleton, the neurosecretory cells in the brain are activated. These cells trigger the release of other hormones which eventually stimulate the prothoracic glands to secrete moulting hormone (ecdysteriods).

The primary function of moulting hormone is to stimulate the epithelial cells in the cuticle to begin the synthesis of a new exoskeleton.

In immature insects, juvenile hormone is secreted by the corpora allata prior to each moult. Juvenile hormone ensures that the insect remains immature by inhibiting the development of adult characteristics such as wings and reproductive organs.

During the last larval or nymphal instar, the corpora allata shrink and stop producing juvenile hormone. This allows the development of adult characteristics to proceed and causes the insect to moult into an adult or a pupa that will metamorphose into an adult.