The Effect of Temperature on Locust Flight Muscle

Abstract

In a recent study of the motor activity in relation to the wing movements of flying desert locusts, muscle action potentials were used to indicate mechanical activity of single motor units and also to demonstrate the motor repertoire of the central nervous system at the unit level (Wilson & Weis-Fogh, 1962). In order to do this it was essential to know exactly how the recorded potentials are related to the mechanical response at the relatively high thoracic temperature of flying locusts, 30–42° C. ; this information is provided here. During flight at medium intensity most muscles are fired a single time per stroke cycle and the movements are based upon ordinary twitch activity, but in some control reactions and during more powerful flight, D. M. Wilson discovered that locusts often make use of double firing, i.e. a unit is fired by two closely spaced action potentials (in the locust normally 4–8 msec.). In cases where the tetanus : twitch ratio is higher than unity this can obviously result in more force and power and he suggested that this may provide an important control mechanism in such systems which operate essentially on a twitch basis (Wilson, 1960). It was therefore of interest to investigate the mechanical effect of double firing.