Figure 31.10: The Tracheal Breathing System of Insects (A) The insect breathing system consists of elaborate arrays of branching, gas-filled tubes called tracheae, which open to the atmosphere through pores called spiracles. In many insects, air sacs connect to the tracheae and can act as bellows to cause tracheal ventilation. (B) The spiracles of a Pandorus sphinx moth larva are visible on the sides of its body. (C) This scanning electron micrograph shows an insect trachea dividing into smaller tracheae and tracheoles. All cells in an insect’s body are close enough to one of these branches to receive O2 directly from the tracheal system by diffusion.