Fig. 3 . Morphology and movement of the wing hinge area. (A) Tegula position in the folded (left) and unfolded (right) forewing, frontal view. mssc, mesothoracic scutum; mtsc, metathoracic scutum; tg, tegula; lg, ligament; 1ba, first basalar sclerite; eps, episternum; sc, subcosta; scmf, subcostal membrane fold (also for B—D). The tegula is integrated into a common ligament (lg, blue shading) attached to the basalar sclerite, scutum, subcosta and leading edge of the wing. During the downstroke, the organ slides into a subcostal membrane fold, indicated by a dashed circle (see Fig. 1Diii). (B) Schematic drawing of the forewing hinge in dorsal view (the diagram on the left indicates the area shown). The posterior displacement of the scutum (black arrow) and synchronous rostral stroke deviation (white arrow) of the wing near the lower stroke reversal are indicated by reference lines; the change in the orientation of the first basalar sclerite is indicated by a green arrow. See text for details. fw, forewing. (C) Displacement of mesothoracic wing hinge components during the wingbeat cycle; three consecutive cycles are shown. The upstroke phase of the forewing is indicated by the shaded area. AEP, anterior extreme position of movement; PEP, posterior extreme position of movement; URP, upper reversal point; LRP, lower reversal point of the wing (see also Fig. 1C). (D) Displacements of the meso- and metathoracic scuta in relation to fore- (fw) and hindwing (hw) movements; three consecutive wingbeat cycles are shown. The upstroke of the hindwing is indicated by the shaded areas.