Insect molting is to meet the needs of its own growth. The exoskeleton of insects is composed of wax layer and chitin layer. The wax layer is located at the outermost edge of the exoskeleton, which can prevent the evaporation of water in insects. Chitin layer is the main component of exoskeleton. Below it are epidermal cells that can secrete exoskeleton components. Once the exoskeleton components secreted by epidermal cells are hardened, they can not continue to expand, which limits the growth of insects. Therefore, insects molt due to growth changes in the process of growth and development. When molting, epidermal cells secrete an enzyme to dissolve the chitin layer, and the wax layer will break, so that insects molt a layer of skin. At the same time, epidermal cells will re secrete exoskeleton components, and the insect body will grow and develop before the new exoskeleton is completely hardened.