The activity of pleurodorsal muscles during flight and at rest in the moth Manduca sexta (L.)

In the moth Manduca sexta, the paired mesothoracic flight steering muscle II PD2m takes part in the generation of the flight rhythm and is spontaneously active in the non-flying animal. This spontaneous activity is modulated by optomotor stimuli and directionally selective. The directional response characteristics are analyzed. Another spontaneously active steering muscle pair, the III PD2c, is situated in the metathorax. The activities of this pair and of a third muscle pair, the III PD3 are also influenced by visual stimulation.The responses of all 6 muscles to optomotor stimuli which simulate the flight situations yaw, roll, thrust and lift are analyzed. Each situation elicits a unique pattern of activation/deactivation within this set of muscles. The activity pattern in non-flying animals allows the prediction of flight steering mechanisms such as changes of wing area in flight turns and provides a useful basis for the analysis of visuo-motor pathways.