Different groups of animals have different specialized respiratory organs. But there are only three basic types. All three types involve thin-walled moist areas where an exchange of gases can take place.
All members of the insect family breathe using a system of air ducts or tubes called tracheae (singular, trachea). The same word is used for the single windpipe of larger animals, including Man. The tracheae pass into the animal's body from external openings. They divide and re-divide, and reach all parts of the animal's body.
Tracheae are directly in contact with the tissue cells. The other two types of respiratory organ are supplied with many blood vessels. Oxygen passes into the blood and is then carried to the tissue cells.
All members of the insect family breathe using tracheae. On the sides of an insect's body, above its legs there are openings called 'spiracles'. These are the entrances to the network of tracheae within the body.
Movements of the insect's body cause air to be pushed through the spiracles into the tracheae. The air is not brought into contact with a blood system as happens in gills and lungs. It travels to the ends of the tracheae and there is direct exchange of gases between the tissue cells and the air in the tubes.
