In the metamorphosis process of cicada, the insects of LEPIDOPTERA (that is, butterflies, moths, cicadas, etc.) hatch early because of insufficient nutrients in their eggs, and the hatched larvae must undergo complete metamorphosis with great changes before they can be transformed into adults. This juvenile insect is called a larva (such as the cicada body that we are familiar with). The larva develops into a pupa first and then becomes an adult. In the later stage of embryonic development, if one insect state changes to another, or if the same insect state has a previous age and meets a later age, (cicada molting belongs to the latter) it must be molted once. The number of molting varies with different insect species, and cicadas molt four times. In fact, molting is a very common phenomenon in the insect world. (For example, maggots of flies) The "skin" of cicadas is actually its exoskeleton. Insects don't have an endoskeleton like humans, so they have to rely on a hard exoskeleton composed of chitin to support and protect their bodies. But the hardened exoskeleton can't grow with the growth of the body, so when the insect body grows up, it must take off the narrow layer of "skin" before it can continue to grow. This is actually similar to the snake's molting. I don't know if you have any experience in raising cicadas, or you can find that the skin looks a little transparent some time before it is about to shed its skin, and something seems to be moving inside. This is that the body inside it has grown up, but the skin can't cling to the body as it used to! It's molting! When the old exoskeleton is taken off, the new exoskeleton is soft and can grow with the body. After a period of time, it will harden and become an exoskeleton that can't continue to grow. When it continues to develop and grow, it will molt again until it becomes a pupa and then an adult.