Fig. 7. A pulse of sound is generated during a kick. (A) Recordings to show the level of sound that is generated in different kicks by a single locust if the tibia is allowed to extend only to the angle indicated. No sound is produced if extension is prevented at 20°, and only a faint sound occurs when extension is prevented at 50°. (B) The timing of the sound pulse relative to movements of the tibia (circles) and distortions of a semi-lunar process (squares) in an individual kick. The sound begins only when the semi-lunar process is unfurling and when the tibia is already extending. Measurements were made from images captured at 1000 s^–1.