The Control of Walking in Orthoptera

The patterns of leg movements during normal straight-line walking of the locust Schistocerca gregaria and the grasshopper Romalea microptera were recorded and analysed. The ratio of protraction to retraction increased with walking speed except in the prothoracic legs. At any one speed both protraction and retraction durations were variable but the variation was greatest for protraction. The locust employed an alternating tripod gait at all walking speeds recorded (2–8 steps/sec.) It displayed a high level of variability in its leg movements which appeared to be held in check by stabilising mechanisms operating on the first and last leg pairs. The movements of individual legs of the grasshopper were very similar to those of the locust but the gait used was not alternating tripod. Comparisons were made with other insects and it was suggested that the specialization of the metathoracic legs in the locust gave rise to most of the variability in leg movements and that the relative independence of the prothoracic legs reflects an exploratory role in walking.