What is the site of gaseous exchange in an insect?

• Gaseous exchange in insects occurs within the tracheal system, a network of air-filled tubes that deliver gases directly to body tissues

• Air enters and exits through external openings called spiracles, located along the thorax and abdomen; these level muscular valves help prevent water loss

• From spiracles, air travels through larger tracheae, which branch into finer tubes known as tracheolesIt is primarily at the tracheoles—tiny (~1 µm diameter), thin-walled structures often contacting cells directly—that the actual exchange of oxygen and carbon dioxide occurs

In summary:
Oxygen diffuses from air through spiracles → tracheae → tracheoles → directly into tissues.
CO₂ follows the reverse path back to the exterior via tracheoles → tracheae → spiracles.