Spiracular Control - Respiration
Another very interesting system of spiracular control is seen in some insect species. The spiracles are kept closed tightly most of the time. When the insect requires oxygen the spiracles open partially and close rapidly again. This 'fluttering' of the spiracle lets the air enter in a streaming movement without much loss of water.
Once a high partial pressure of oxygen is reached the spiracles close. While the oxygen is utilised by the tissues the carbon dioxide is stored temporarily in the tissues as bicarbonates thus keeping the Pco2 within tolerable limits, when Pco2, reaches a critical limit the spiracles open fully and expel the carbon dioxide in a single burst and the cycle is repeated.