Tracheal Gills - Respiration

In many species of aquatic insects the air in the trachae is replenished by diffusion of oxygen via tracheal gills. Many aquatic insects carry a temporary store of air as a bubble on the body surface which replenishes the air in tracheae during submergence. In other aquatic insects a constant volume of air is held as a thin layer close to the body surface by water repellent hair forming a plasteron (or layer of air).

As long as water is well aerated insects with plasteron can remain submerged for many months. As much as one-third or half of the total capacity of the air system can be emptied in one expiration giving a renewal of about half the volume of the respiratory system. This is much greater than in a mammal at rest, where in each breath only 1/5 of the air contained in the system is renewed.