A working hypothesis for the control and dynamics of rapid flight maneuvers begins to emerge from an analysis linking aerodynamics, biomechanics, and neurobiology (Fig. 5). As a fly explores its sensory landscape, specialized expansion-sensitive circuits in the visual system detect obstacles and initiate all-or-none body saccades. Descending interneurons carry a trigger signal to the thorax that activates the motor neurons of a small set of steering muscles. Because the changes in wing motion required to steer are so subtle, they are probably brought about by small shifts in firing phase, which function to adjust the dynamic stiffness of muscles and alter the transmission mechanics of the wing hinge. The resulting changes in wing motion, though minor, are large enough to generate sufficient torque to turn the animal away from the looming obstacle. After only 4 or 5 wing strokes, the halteres detect this angular motion and trigger a compensatory counter-turn that decelerates the animal and terminates the saccades after a rotation of only 90°. Collectively, these results provide an important basis for future research on the control of insect flight, as well as insights for the design of biomimetic flying devices.
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