Because when an arthropod sheds its skin, its new skin underneath is very soft, so the animal can grow once it's free of its hard armour. They're easy squishy prey during this period. They're only safe once the new skin hardens again.
Oh, not to mention the process itself often renders them immobile. Some (Spiders etc) have to lie on their backs for hours while taking off their 'panties'.
When arthropods outgrow their exoskeletons, they undergo periods of molting. During molting, an arthropod sheds its entire exoskeleton and manufactures a larger one to take the smaller ones place. Molting is controlled by the arthropods endocrine system. An animals endocrine system regulates body processes by means of chemicals called hormones. As the time of molting approaches skin glanes digest the old part of the exoskeleton and other glands secrete a new skeleton. Whenthe new skeleton is ready the animal pulls itself out of what remains of the original Skelton, this process can take several hours while the new exoskeleton is still soft the animal fills with air or fluids to allow room for growth before the next molting. Most arthropods molt several times between hatching in adulthood. This process is dangerous to the animal because it is vonerable to preditors while their shell is too soft to protect themselves. Most arthropods like to hide during molting or molt at night when less predictors can get them.
Because they might get murked. And that is never good
Most only do so in larval/juvenile stages, when it's time to grow. Some arthropods such as tarantula females continue growing and molting until death. Also, when damage has occurred (torn off leg for example) molting can be induced earlier to develop and grow new appendages. :)
Its exoskeleton, or 'armour'. A new one has already grown underneath it as molting begins, and only needs some time to harden out afterwards.
The appropriate time to provide extra care for a leopard gecko molting is when you notice that it is shedding its skin. This process can be stressful for the gecko, so it is important to ensure that it has a humid hide, proper hydration, and a calm environment to help it through the molting process.
Molting in crayfish is dangerous because it leaves them vulnerable to predation and environmental stress. During this process, they shed their old exoskeleton and are temporarily soft-bodied, making them less capable of defending themselves. Additionally, their new exoskeleton takes time to harden, during which they are at risk of injury and infection. This critical period requires careful navigation of their surroundings to avoid threats.
Molting, or shedding their skin, is a natural process for anoles and typically does not cause them pain. During this time, they may experience some discomfort as their old skin loosens, but it is generally not harmful. Anoles may become less active or seek hiding spots while molting, which is a normal behavior. Proper humidity and care can help facilitate a smooth molting process.
Replacing its feathers
Birds typically go through the process of moulting or molting in the late summer or early fall, after the breeding season. During this time, they shed old feathers and grow new ones to prepare for the upcoming winter.
When crayfish outgrow their shells, they undergo a process called molting, where they shed their old exoskeleton to allow for growth. During this process, the crayfish may become vulnerable to predators, as it takes time for the new shell to harden. After molting, the crayfish will gradually develop a larger, more robust exoskeleton. This cycle of growth and molting is essential for their survival and development.
Horses may experience fatigue during molting season due to the energy required for growing a new coat. They may also feel itchy and uncomfortable, which can affect their energy levels. Providing adequate grooming and nutrition can help support horses through the molting process.
Birds and reptiles both do. Some insects and arachnids molt. Birds molt feathers from time to time. Reptiles molt their top layer of skin. Animals with exoskeletens, such as hermit crabs, also molt.