Ecdysis

Some arthropods, especially large insects with tracheal respiration, expand their new exoskeleton by swallowing or otherwise taking in air.

The maturation of the structure and colouration of the new exoskeleton might take days or weeks in a long-lived insect; this can make it difficult to identify an individual if it has recently undergone ecdysis.

[5] In preparation for ecdysis, the arthropod becomes inactive for a period of time, undergoing apolysis or separation of the old exoskeleton from the underlying epidermal cells.

For most organisms, the resting period is a stage of preparation during which the secretion of fluid from the moulting glands of the epidermal layer and the loosening of the underpart of the cuticle occurs.

Then, by crawling movements, the organism pushes forward in the old integumentary shell, which splits down the back allowing the animal to emerge.

Endopterygotes have more alternatives to moulting, such as expansion of the cuticle and collapse of air sacs to allow growth of internal organs.

Spiders generally change their skin for the first time while still inside the egg sac, and the spiderling that emerges broadly resembles the adult.

The physiological processes of releasing the old exoskeleton from the tissues beneath typically cause various colour changes, such as darkening.

Most species of spiders hang from silk during the entire process, either dangling from a drop line, or fastening their claws into webbed fibres attached to a suitable base.

The carapace lifts off from the front, like a helmet, as its surrounding skin ruptures, but it remains attached at the back.