Figure 2.

Motor patterns that drive flight in locusts and other neurogenic insects. (A) Two sections of typical flight motor output recorded as muscle action potentials in a flying locust, from Waldron (1967). Electrodes in a wing elevator (elev) muscle and a wing depressor (dep) muscle recorded alternating spikes from these antagonistic muscles. Since transmission from the motor neurons to each muscle is one-for-one (Wilson and Weis-Fogh, 1962), these recordings report each spike in the motor neurons that innervate each muscle. These two sections of a continuous recording were separated by several seconds during which the locust increased its power-output by increasing its wing-beat frequency and increasing the numbers of spikes each neuron fired in a cycle from one to two or three spikes. (B) Wilson's diagram of the locust flight motor pattern assembled from recordings from forewing and hindwing flight muscles, plotted along with the elevation of each wing (Wilson, 1967). The cartoons of the flying locust show the wing positions at maximal elevation and depression of the fore- and hindwings. (C) Simultaneous recordings from an elevator (elev) and a depressor (dep) muscle in an locust whose wings and all wing proprioceptors had been removed (cartoon). In response to a steady wind directed toward the animal's head, the motor neurons that innervated these muscles began to fire in the characteristic flight pattern, although at a lower wing-beat frequency than would an intact locust. Reproduced from Wilson (1964)