Sound production and hearing in the cicada,Cicadetta sinuatipennis osh. (Homoptera, Cicadidae)

Summary

• 1. The spontaneous song ofCicadetta sinuatipennis males consists of alternating tymbal sound production and wing-clicking (Fig. 1). The temporal and spectral characteristics of tymbal and wing sounds are unalike (Table 1, Fig. 7).

• 2. Wing-clicking is the result of sudden lateral movements of the forewings. A click is generated by the outward buckling of a specialized caudal margin of a forewing which is locked in a narrow groove on the scutellum before sound production (Fig. 2).

• 3. Central projections of auditory and motor fibres with axons in the tympanal and tensor nerves were shown with the help of axonal cobalt iontophoresis (Figs. 3–5). The anatomy of the large tymbal motor neuron and three tensor motor neurons with ventral cell bodies is described.

• 4. Stimulus thresholds for the summed response of primary auditory fibres were measured for different sound frequencies. The resulting hearing curves show that the auditory organs have a sharp peak of sensitivity near 6–6.5 kHz. When stimulated by the natural spontaneous song of a male, the ear gives clear “on”-responses to each click of a wing sound with thresholds of about 21–31 dB SPL and very weak asynchronous reaction to tymbal sounds with thresholds of about 70 dB SPL. This is a result of the different spectral content of these sounds (Fig. 6, 7). It is suggested that wing sounds are used for long-range communication between males and females. Tymbal sounds can be used only for short-range communication or have another, possibly repellent function.