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. In its simplest form the spiracle is a simple opening into the tracheal system. Usually the entrance is lined with hairs to keep out the dust. In most terrestrial insects, however, the spiracle is capable of opening and shutting. Spiracles are generally kept open for shortest amount of time possible to prevent water loss.