Fig. 1. Living components of butterfly wings.

a Photo of a male painted lady butterfly, Vanessa cardui. b Photo showing mechanical sensilla (indicated by blue arrows) near the wing margin of an adult V. cardui, including two disc-shaped campaniform sensilla and two hair-shaped bristle sensilla. c Photo showing nerve fibers and mechanical sensors, stained with methylene blue, in the cubital veins of the forewing of an adult V. cardui. Regions in the dashed frames are enlarged in d and e to show, respectively, one bristle sensillum and one campaniform sensillum as well as associated somata (or cell bodies) and axons. f Two snapshots of a video to show variation in the width of the hemolymph channels in the medial vein of the right forewing of an adult V. cardui. g Observed variation in hemolymph channel width (black solid curves) and instantaneous hemocyte flow velocity (red circles) as a function of time for individual V. cardui butterflies at three different ages (3, 8, and 24 days after eclosion). Positive sign of flow velocity indicates movement of hemocytes from the base toward the tip of the wing; negative sign indicates movement of hemocytes from the tip toward the base of the wing. Supplementary Movie 3 shows tidal flow of hemolymph in a radial vein of V. cardui. Source data are provided as a Source Data file.