(A–D) Artificially selected blue J. coenia. (E–H) Wild-type J. coenia. (I–L) J. evarete, blue male from Bolivia. (M–P) J. evarete, brown male from Jamaica. (Q–T) optix mosaic knockout mutant (mKO) in J. coenia. (A,E,I,M,Q) Dorsal hindwing, red arrowhead indicates the characterized scale’s location. (B,F,J,N,R) Scale in the orientation it would occupy on the wing, showing the abwing surface of the cover scale. Black scale bars are 25 µm. (B’,F’,J’,N’,R’) Adwing surface of cover scale, showing the underside of the lamina. (B”,F”,J”,N”,R”) Dissected scale with arrow showing regions where all ridges and crossribs are removed to expose the bare lamina. The lamina is sufficient to create iridescent blue and gold structural colors. (B”’,F”’,J”,N”’,R”’) Scale immersed in fluid with a refractive index matched to chitin, thus eliminating reflection to show only pigmentary color. Blue and brown scales have comparable amounts of a brown pigment. (C,G,K,O,S) Helium ion micrograph of cross-sectioned scale. Each lamina is colorized, with approximate thickness indicated by an adjacent red bar (precise measurements were taken at sites chosen as in Materials and methods). White scale bar is 500 nm and applies to all HIM images. (D,H,L,P,T) Reflection spectra for the adwing surface of disarticulated scales. Solid line is the mean spectrum, and blue envelope is one standard deviation; minimum N = 3 scales per graph.