The initial wound healing response consists of a pulse and flow of actomyosin and a synchronized wave of apical cell constriction. (Ai) Movie stills of a pupal notum expressing UAS-mCherry-Moesin driven by pnr-GAL4 show a flow of increasing actin accumulation, which is visible in the early minutes of wound healing and culminates in cable formation. Time after wounding is indicated in the panel’s top left corner. (Aii) Graphic representation of the actin flow according to a color-coded time scale. The time when each pixel reaches its maximum actin intensity is color coded, ranging from early time points in dark blue to latter time points in dark red. A wild-type flow is represented by a gradient of colors, dark blue in the periphery (early maximum actin intensity) and red at the leading edge (late maximum actin intensity). Bar, 10 µm. (Bi) Movie stills of an epithelium expressing mCherry-Moesin and Sqh-GFP show that after injury actin and myosin flows progress toward the wound. Dashed lines indicate the wound margin. Horizontal line indicates the xz kymograph area shown in Fig. 2 Bii. Bar, 5 µm. (Bii) xz kymograph shows that the myosin follows the actin flow in the early minutes of wound healing. White arrowheads indicate the position of the maximum of myosin intensity at each time point. Both flows are apical and culminate in the formation of the actomyosin purse-string (yellow arrowhead). Bars: (x) 5 µm; (z) 2 µm. (C) Movie stills of the early stages of wound healing in a pupal notum expressing E-cadherin–GFP. A wave of synchronized cell constriction can be seen starting as early as 200 s after wounding and rapidly progressing toward the wound margin. Cells highlighted by white arrowheads are at the leading edge of the contraction wave. The magenta line represents the previous frame superimposed on the actual frame (green). Time after wounding is indicated at the bottom of each panel. Bar, 5 µm.