Solution: The trachea is an insect’s respiratory organ. Air enters the trachea through spiracles, which are small apertures. Spiracles can be seen on either side of the insect’s abdomen. Each segment of the abdomen has a pair of spiracles. The trachea also branches into smaller tubes until it reaches tissue level. Diffusion exchanges the oxygen that enters the trachea with the tissues. Carbon dioxide from the tissues that enter the trachea is driven out of the body at the same time.