Figure 14.

Timeline of the wingbeat of Eristalis, showing the similarities in the gear change mechanism measured by Nalbach [1] for Calliphora and the changes in alula state and wing kinematic measurements presented here. During the wingbeat, the gear change comes into effect when the radial stop (RS) contacts the pleural wing process (PWP) at mid-downstroke, and lasts until early upstroke. The alula changes state at the same time as the radial stop contacts the pleural wing process. This is also the time at which the angle of incidence and stroke angle change according to the state of the alula. The timing of supination is also altered, but the timing of pronation is outside the window where the gear change mechanism operates, and so is unaffected.