Fig. 5. Response index scores permit a decomposition of the active and passive responses. (A) Response index scores were significantly higher in live flies (asterisks) than in dead, winged flies at velocities below 0.8 m s^–1. (B) The percentage of the response attributable to the aerodynamic effects of wings was quantified by subtracting the mean response index for dead wingless flies from the corresponding values for dead, winged flies and dividing by the mean, dead, winged response (filled circles). The effect of the live behavioral response was similarly quantified from the responses of live flies and dead, winged flies (open circles).