Trachea: Insects
Air is a different medium than water. There is an increase in oxygen and carbon dioxide concentration, and oxygen diffuses much quicker than in water. The respiratory surface, which must be large and moist, always loses water through evaporation. A solution to this problem is to have a respiratory surface that has many folds in the interior of the body.
Trachea are tiny air tubes throughout the insect’s body. The tiniest tubules extend to almost every cell, where the gas is exchanged by diffusion across a moist membrane. The opening into the trachea is a spiracle. Air can enter the trachea through diffusion or rhythmic body movements.