Correlations between aerodynamic output, electrical activity in the indirect flight muscles and wing positions of bees flying in a servomechanically controlled wind tunnel

Abstract

1) Bees hanging on an aerodynamic two component balance were placed in front of a laminar wind tunnel. They controlled the wind velocity in the tunnel through a servo-mechanism that held the wind velocity to exactly the opposite of the flight speed, thus selecting lift and thrust freely. The parameters lift, wind velocity, occurrence of action potentials in the indirect dorsoventral flight muscles (DV) and indirect dorsolongitudinal flight muscles (DL) and body temperature were measured. The correlations were analysed (Fig. 1). 2) The lift is positively correlated to the body angle (angle between body length axis and wind tunnel length axis), the flight speed is negatively correlated to the body angle (Fig. 2). 3) Action potential frequencies in both muscle groups exhibit a strong positive correlation to the lift (Fig. 3). Changes in action potential frequencies and lift run parallel with a delay of less than 200 msec (limitation imposed by measuring system). Different motor units in a given muscle have different absolute discharge frequencies (Fig. 4). 4) A pronounced synchronization between wingbeats and action potentials in the indirect dorsoventral muscles can always be found. 5) Randomly triggered photographic pictures show the wings most frequently at the lower turning point. Exposures that were triggered by action potentials in the dorsoventral indirect flight muscles display this wing position significantly more frequently (Fig. 5).