The exoskeleton of cockroach is rigid, yet the body can bend a little between the body segments due to
dorsal tergites which are pigmented
arthrodial membranes which are flexible
ventral sternites which are chitinous
lateral pleurites which connect tergites and sternites
The sclerites are jointed to one another by arthrodial membranes which are flexible. This allows some bending of the body between the segments.