Each Chrysina elytron stacks ~70 transparent cuticle sheets; the colour is interference, not pigment — which is why it never fades in a drawer.
Tighten the stack and green shifts toward C. resplendens gold; loosen it and you read copper-red — same beetle chemistry, different geometry.
C. gloriosa adds a chirped helicoid that polarises light — the silver sheen is a left-handed mirror, unique among visible-band animals.
Structural colour means the label outlasts the ink: a typeset ID card and a black-foam grid keep a 1920s specimen exactly as bright as it was pinned.