Complex sentence: In preparation for ecdysis the arthropod will become inactive for a period of time, and then by crawling movements pushes forward in the old integument, which splits down the back allowing the animal to emerge.
Split into simpler sentences: In preparation for ecdysis the arthropod will become inactive for a period of time. Then, by crawling movements, it pushes forward in the old integument, which splits down the back allowing the animal to emerge.