Fig. 4 . Movements of the tegula during the wingbeat cycle. (A) The forewing hinge in frontal view; schematic drawings of upper (left) and lower (right) stroke reversals. Abbreviations as in Fig. 3. The dashed line marks the longitudinal axis of the tegula organ; rotational movement around this axis is indicated by an elliptical red arrow. Black arrows indicate displacement of the scutum and the change in orientation of the basalar sclerite. (B) For four wingbeat cycles of the forewing (Bi) and the hindwing (Bii), the time courses of tegula rotation and inclination are shown in relation to stroke position and stroke deviation of the wing. (C) Displacement of the tegula organ in the horizontal plane during the wing stroke (data from four consecutive wingbeat cycles superimposed). The black arrow marks the direction of movement during the downstroke; the white arrow indicates upstroke. URP, upper reversal point; LRP, lower reversal point of the particular wing; AEP, anterior extreme position of movement; PEP, posterior extreme position of movement.