Jewel beetle: The metallic rainbow that never fades

The jewel beetle is the "gem" of the beetle world. Its shell carries a metallic sheen, polished like a rainbow, and is truly dazzling. That brilliance is not painted on — it is made by fine structures on the body surface. Because it does not fade, people even used the wing cases to inlay treasured objects.

Its body

The wing cases (elytra) of the jewel beetle carry a layer of nanometre-thin structure. As light bounces back and forth between these layers and interferes, it creates that metallic rainbow. Because this "structural colour" is not made with pigment, it does not fade even after a long time as a specimen. In Japan, the Tamamushi Shrine of Hōryū-ji temple was inlaid with tens of thousands of jewel-beetle wing cases — still gleaming after a thousand years.

Its larvae bore through dead or weakened wood, while the adults visit summer flowers to sip sap and pollen.

Its life and its remarkable habit

Some jewel beetles have a truly surprising ability: they can sense the infrared heat given off by forest fires and fly straight to freshly burned woodland to lay eggs — because that is just where the "nursery" for their larvae is. That "fire-chasing" instinct is one of nature's most unusual adaptations.

A note for grown-ups

You could talk with a child about "can colour last forever?": the jewel beetle's colour, made by structure rather than pigment, is what truly never fades. Asking a child to look for other "physics-based colour changes" around them is a lovely first lesson in science.