Fig. 3. (A) The wingbeat frequency, f, decreases with increasing flight speed, U, from 9.1 Hz at 8.0 m s^–1 to 8.3 Hz at 9.2 m s^–1. (B) Upper (u), lower (d) and total (tot) angular excursion, , of the wing in the vertical plane as a function of flight speed, U. The increase in _tot(U) comes only from the increase in _u(U). (C) Amplitude, A, normalized by mean chord length, c. (D) The downstroke duration, T_d, increases with flight speed, U. The downstroke fraction, , does not vary with flight speed, U. (E) The wing angular velocity at mid-upstroke and -downstroke, , does not vary greatly with flight speed, U. (F) Wing semispans, b_u,d at mid-upstroke and -downstroke normalized by mean chord length (c) vs flight speed, U. Wing semispan does not vary with flightspeed. The span ratio, R, does not change with flight speed, U. Error bars represent ±s.e.m.