In the metamorphosis of LEPIDOPTERA (butterfly, moth, silkworm, etc.). ), due to the lack of nutrition in the egg, the embryo hatches early, and the hatched larvae must undergo a great change of complete metamorphosis before they can be transformed into adults. This kind of larva is called larva (such as the well-known silkworm body). Larvae first develop into pupae, and then become adults. In the later stage of embryonic development, when one insect state changes to another, or when the same insect state has the previous age and meets the latter age, it is necessary to molt once. The number of molting varies with different insect species, and the silkworm molts 4 times. In fact, molting is a very common phenomenon in the insect world, such as maggots of flies. The "skin" of silkworm molting is actually its exoskeleton. Insects don't have an endoskeleton like humans, so they must rely on a hard exoskeleton made 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 "skin" to continue to grow. This is actually similar to a snake molting. I don't know if you have any experience in sericulture, or you can find that the "skin" looks a little transparent some time before molting, and something seems to be moving inside, indicating that the body inside has grown up, but the "skin" can't cling to the body as before! 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 cannot continue to grow. When it continues to develop and grow, it will shed its skin again until it becomes a pupa and then an adult.