NEURAL CONTROL OF SOUND PRODUCTION IN MINGMING CICADA

A new kind of sounding nerve(SN) construction in cicadas and the effec t exerted by the thoracico-abdominal ganglia on the calls are describe d. The obtained results lead to a new understanding of the neural cont rolling mechanism. of the sounding movement in cicadas. In the Mingmin g cicada (Oncotympapa maculaticollis Motsch), the SN is a complex nerv e, the giant axon is about 20 mu m in diameter and contains some axons of about 1-5 mu m in diameter, which are separately encircled by mult i-layer measaxons. The latent periods of the sound-productions induced by electrostimulations of the SN an (10.3+/-1.2) ms on an average. Th e innervation of SN on sounding movements of the sound muscle (SMc) is possessed of the complex characteristics, and the prepotential of its three-phase action potential presents obviously a bipeak structure. T he latent periods of myoelectricities and calls produced by the discha rges of SN exciting SMc are (5.8+/-0.5) ms and (11.2+/-1.2) ms, respec tively. The accessory sound nerve being closed up to the SN goes downw ards to the anterior end of SMc and separates from SN, then it shaves through an inside-lateral muscle membrane of SMc and turns to the open -close muscle of the sound door. No significant effects on the time pa ttern and the twitching property of the sounding movements of both lef t and right SMcs are found after removal of the brain. Removing the pr othoracic ganglion remarkably affects the time pattern of sounding mov ements of the SMc, but not the twitching property. Removal of half of the mesothoracic ganglion, however, exerts significant effects on both duration and twitching. It on be seen that the sounding movements of the left and right SMc may also be regulated and controlled by the pro thoracic and mesothoracic ganglia.