Arthropods are a group of animals that all have a hard outer covering called an exoskeleton. The reason for this is that it protects the species from any predators or harmful things in their environment. This type of animal is probably the most bountiful of all other types. They include ladybugs, who have a shiny, tough back, crabs who infamously have a hard shell, and many others. Exoskeletons can come in various shapes or sizes, but no matter what, the hard exterior will always be made out of fibrous material known as chitin. Since they all have the exoskeleton, the only way for these species to grow and develop is by shedding their skin. Here's why.
Shedding skin is a natural process that occurs for arthropods. When these animals start to get older, a process known as ecdysis begins to occur. This is when the hormones are triggered, and the skin of the animal starts to molt away. Both the outside layer of the exoskeleton, known as the cuticle, and the inner, the epidermis, start to form a new layer. The next step in the process is controlled by the animals breathing - as they begin to take in an abundance of air, the fluid in the body starts to move around until they crack a suture.
This process, for example, occurs in cockroaches as they “split right down the middle of their backs” and “pop out maybe in 20 minutes or less,” explained Andrine Shufran - an entomologist at Oklahoma State University. But when it comes to those who live in water, like crabs, they take in water instead of air which places pressure on the seam of their bodes. Eventually, that pressure causes the Aquatic crustaceans to be pushed out of their old shell and reveal a new layer of skin.
Another reason why these animals say goodbye to their former skin is to get rid of ectoparasites, aka organisms that live on top of their skin. Some insects, such as Madagascar hissing cockroaches, even go as far as to eat their own exoskeleton. "It's good to hide any evidence that you're around," Shufran explained, "but it also is a way to conserve all the energy that you've already put into your previous existence."