The woodlouse has a shell-like exoskeleton, which it must progressively shed as it grows. Adult woodlice lose their armor or exoskeleton approximately once every four weeks. Firstly the back half is shed and about twelve hours to three days later the front half. They eat their own exoskeleton, because it contains a lot of chalky nutrients.

The individual on this image is sitting on a Trembling merulius, phlebia tremellosa.