Response Modification by the Central Flight Oscillator of Locusts

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Abstract
Flying locusts respond to changes in wind-velocity or wind-angle with abdomen posturing in the vertical or horizontal plane, respectively. Receptor hairs on the head sense these wind parameters and evoke the responses in specific abdominal muscles. Records were made from individually identifiable motoneurones to these muscles during the performance of wind-evoked behaviour. During flight these motoneurones are excited by the central flight oscillator and show a burst rhythm at flight frequency. Wind stimuli modulate the number of spikes per burst in this rhythm, but do not affect its frequency or phase with respect to the wingbeat. Changes in wind-velocity and wind-angle evoke different relationships of muscle synergy and antagonism, resulting in the two different patterns of behaviour performed by the same group of muscles. During flightless periods the motoneurones show no flight rhythm, but only the much lower frequency ventilatory rhythm. At these times they are unresponsive to wind stimuli.