Pterin and carotenoid pigments are located throughout the tissue of the dewlap, creating yellow and red hues.[5] Lizards usually accompany dewlap movement with head bobs and other displays. The dewlap moves through extension and contraction. The muscles creating this movement are the ceratohyoid muscles and are connected to the hyoid apparatus in the throat and larynx area.[6] Though the purpose of these displays is unclear, the color of the dewlap and the head bobs are thought to be a means of contrasting background noise.this is unintelligible[clarification needed]