Motor Patterns Underlying Pheromone-Modulated Flight in Male Moths, Manduca sexta

Abstract

Male moths typically find mates by flying a characteristic zigzag path up a plume of sex-pheromones released by a conspecific female. This upwind path results from a combination of self-steered maneuvers and continuous reactions to visual, olfactory, and mechanosensory inputs during flight. To characterize motor patterns underlying these flight maneuvers, we have simultaneously video-recorded the orientation tracks, and recorded electromyograms (EMGs) from flight muscles of male Manduca sexta flying freely in a plume of female pheromones. EMG activity was synchronized with video recordings of zigzag flight tracks in a laboratory wind tunnel. The activity of up to five muscles was recorded: (1) the left dorsal longitudinal muscle (DLM), the principal wing-depressor; (2 and 3) the left and right third axillary muscles (AxM), thought to be “steering” muscles; and (4 and 5) the left and right first basalar muscles (BaM), which generate lift and thrust by altering the angle of attack of the fore-wing. Parameters measured from the EMGs were: burst period (ms), and burst duration (ms) for all five muscles; and the time of onset of AxM and BaM activity relative to DLM burst onset (defined as the phase of onset).