The main tubes are referred to as tracheae . The tracheae branch into finer structures called tracheoles . These branch throughout the body. The first spiracle supplies the head region, and makes sure the brain is well oxygenated. The spiracles which supply the wing muscles are isolated from the rest of the body.
Spiracles are external openings of the tracheal system.
They are lateral in position and usually on the pleura . The number is reduced in many insects. Dipterous larvae, for example, have only 2 pairs of spiracles. Some insects have no spiracles. This does not mean that they do not have tracheae, only that these do not open to the outside.