Ecdysis means an exoskeleton molt. As the insect grows within its exo-shell, it comes to a point where its growth can exceed the confines of the shell and must shed this outer skeleton and create a new one. In the upper photo, this Stonefly nymph (Megarcys sp.) has recently shed its exoskeleton and appears a translucent pale colour until its new shell hardens and attains the opacity and colour markings as in the lower photo. This change occurs within the day.