Fig. 1. Location of the tegula. Electron microscographs showing dorsal views of the mesothoracic (A) and metathoracic (B) wing hinge of an adult female Locusta migratoria. The locations of the tegula organs are circled; orientation and wing hinge area are indicated by the locust outline (left; lower image margin, body midline). (A) The location of the forewing tegula (tg) in the downstroke position, with the organ located in a fold of the subcostal (sc) membrane; (B) the hindwing organ in the upstroke position. fw, forewing; hw, hindwing; lg, ligament; lba, anterior process of the first basalar sclerite; mssc, mesothoracic scutum (anterior border); mtsc, metathoracic scutum; pn, pronotum. (C) Schematic drawing of the wing tip (black dots) trajectories, reconstructed from the superimposed video frames recorded during three wingbeat cycles by the lateral camera. The upper (URP) and lower (LRP) reversal points of the forewing (fw) and the hindwing (hw) are indicated by open circles. sd, stroke deviation with respect to the stroke plane (indicated by the line connecting the URP and LRP). (D) Dorsal view of the metathoracic wing hinge; pictures are single frames from a high-speed video recording (500 frames s^-1). The tegula organ (circled) is shown in the upstroke (Di) and downstroke (Dii) position (approximate area shown in Di is indicated by the dashed frame in B). The tegulae were marked with black ink dots (open arrows). (Diii) Schematic drawing of the tegula in dorsal view, with the ink dot indicated in black, (a) when the wing was folded in the resting position, (b) at the upper reversal point (URP) of the wing, (c) in the horizontal wing position (mid-downstroke) and (d) at the lower reversal point (LRP) of the wing. The arrow indicates the longitudinal axis of the organ, pointing towards the wing tip. The instantaneous angle of tegula rotation was measured as the orientation of the small bisector (line marked by a dot) of the ink dot ellipsoid in the plane view, with the orientation of the ellipsoid at the upper reversal point of the wing used as a reference. (e) Superposition of b and d showing the total angle of rotation during a wingbeat cycle ().