Many creatures shed their outer layer to grow and develop. This rigid outer layer, an exoskeleton, cannot expand, necessitating its periodic removal. This process is a fundamental aspect of their life cycle, allowing them to increase in size and transform through different developmental stages.
Why Bugs Shed Their Skin
The primary reason many creatures shed their skin is the nature of their external skeleton, known as an exoskeleton. Unlike the internal skeletons of humans, an exoskeleton is a hard, non-living outer covering that provides support and protection but does not grow as the animal grows. As the animal increases in size, the rigid exoskeleton becomes too restrictive.
Shedding, also known as molting or ecdysis, allows for growth spurts. Beyond growth, this process also serves other important biological functions. It enables the repair of damage to the exoskeleton or the regeneration of lost limbs. Molting is also essential for developmental changes, such as metamorphosis, where an organism transforms from a larval or nymphal stage into its adult form.
How Bugs Shed Their Skin
The process of shedding skin, known as molting or ecdysis, is orchestrated by hormones. It begins with the formation of a new, soft exoskeleton underneath the existing rigid one. The inner layers of the old exoskeleton are then partially digested and reabsorbed by the animal, minimizing resource loss.
Once the new skin is sufficiently developed, the old exoskeleton splits along specific lines of weakness, often due to the animal inflating its body with air or water and muscle contractions. The creature then carefully wriggles out of its old skin. The discarded outer layer, a hollow shell, is called an exuvia.
After emerging, the new exoskeleton is soft and pliable. The animal rapidly expands its body before the new covering hardens and darkens. This hardening process provides the necessary protection and support for the next stage of growth.
Bugs That Commonly Shed Their Skin
Many types of arthropods, a large group of invertebrates with exoskeletons, regularly shed their skin. This includes insects, arachnids, and crustaceans.
Common insect examples include grasshoppers, which shed their skin multiple times as nymphs. Cicadas are also well-known for leaving behind their empty brown exoskeletons clinging to trees. Butterflies and moths, during their larval (caterpillar) stages, undergo several molts before pupating and transforming into adults. Bed bugs, in their immature nymph stages, must molt five times, each requiring a blood meal.
Spiders and scorpions, which are arachnids, also shed their exoskeletons to grow. Crustaceans, such as crabs and lobsters, also molt. Soft-shell crabs, for instance, are simply crabs harvested immediately after molting, before their new shell has fully hardened.