MECHANISM OF COUPLING OF LOCUST FLIGHT OSCILLATOR TO OSCILLATORY INPUTS

1. A flying locust responds to a rhythmically flashing light by adopting a wingbeat frequency equal to the flash frequency, if the flash frequency is not too different from the initial wingbeat frequency (Fig. 2). During this response, the wingbeat cycle maintains a particular timing relative to the light cycle (Fig. 1). 2. This oscillator coupling occurs because each light flash, by exciting the elevator motor neurons and/or the depressor motor neurons, causes an acceleration of the flight cycle by an amount that depends on the timing of the flash relative to the flight cycle (Figs. 4 and 5). The phase of the flight cycle relative to the flashes changes until it reaches a value at which the acceleration in each cycle is just sufficient to result in a flight system frequency equal to the stimulus frequency. The resulting constant phase relationship is stable only if slight fluctuations in the timing of the flight cycle are self-correcting. As predicted theoretically self-correction occurs in that portion of the cycle in which later stimuli result in smaller accelerations of the flight cycle. 3. This mechanism of oscillator coupling has been demonstrated by a similar method of analysis for other biological oscillators (Moore et al., 1963; Enright, 1965). It is shown here how the method of analysis can be extended to certain cases of reciprocally coupled oscillators. 4. Some of the data suggest that there may be only one or two layers of neurons in the central nervous network which generates the motor output pattern in flying locusts. © 1968 Springer-Verlag.