You searched for: “air sac
air sac
The thin-walled expansion of the tracheal system of an arthropod, which increases or strengthens the inspiration and the exhalation of air.

Air sacs also give buoyancy to aquatic insects, and in dragonflies, it provides insulation around the thoracic wing muscles.

This entry is located in the following unit: Insects, General Applicable Terms (page 1)