Transduction of mechanical energy into sound energy in the cicada Cyclochila Australasiae

The anatomy of the paired tymbal muscles of Cyclochila australasiae was des cribed. Force-distance relationships of the sound-producing in-out cycle of tymbal movement were measured. The largest forces were measured when the p ush occurred at the apodeme pit on the tymbal plate at angles similar to th e angles of internal pull of the tymbal muscle. Initially, inward movement was opposed by the elasticity of the tymbal, whi ch stored energy. At a mean force of 0.38 N after a mean inward strain of 3 68 mu m, the tymbal ribs buckled, the mean energy release being 45.1 mu J. The energy release occurred over 2-10 ms in three or four sound-producing s teps as successive tymbal ribs buckled inwards. After the ribs had buckled, the force decreased to a mean value of 0.17 N, The force returned to zero during the outward movement, during which the tymbal ribs buckled outwards. The mean energy dissipated in the outward movement was 32.8 mu J. During c ontraction, the tymbal muscle produced mean values for the peak active forc e of 0.31 N over 295 mu m, which gave mean values for the area of the work loops of 47.0 mu J. The calling song of C. australasiae had a mean pulse rate of 234 Hz (117 Hz for each side of the insect). The peak power to mean power ratio for the s ongs was 8.51:1 (+9.30 dB), Measurements of the sound field around tethered insects and of the peak power to mean power ratio of the songs gave values for the mean power of the song of 3.15-7 mW; these correspond to an energy per song pulse of 13.5-30 mu J. Previously reported mean values are 3.15 m W for protest song and 5.1 mW for calling song. The efficiency of transduct ion of mechanical energy into sound energy is between 18 and 46 %.