Abstract: Electromyograms(EMG) of the sounding muscle (SMc) and the synchro call ofMingming cicada were studied parallelly with the aim to reveal the relationship between itstone-varying song and the excitation property of SMc.
In Mingming cicada,the left and right SMc contract alternately,and are the synchronousmuscles in respect of the mode of control. In producing protest songs, the amplitudes. inspontaneous activities,and their pulse widths increase by about 1 ms for the majority. Theamplitudes of the main peak frequencies (MPF) of the second upper partials (UP₂) corresponding to the monopeak EMGs in a synchro call are about 9 dB higher in average thanthose of MPFs of UP₂ corresponding to the dual-peak EMGs. The latent periods of synchrocalls are about 4. 5 ms in average. Moreover, in the process of evolutions of the dual-peak EMGs, a significant negative-correlation between the rising speed of second-peaks andthe amplitude of first-peaks after their fusion is found,i. e. with the increase of amplitudes ofthe first-peak the rising speed of the second-peak decrease with a rate of 3. 4 mV/msin average.