Ground Beetle, China.

With iridescent colours and intricate microsculpture, Carabus ground beetles are some of the most attractive insects. Beyond the resolution of even the most powerful optical lenses are further levels of complexity. The intense colours of this beetle are produced not by pigments but by the interaction of light with separate layers of chitin in the exoskeleton.

These layers can even be preserved in fossils, the colours still present after millions of years. The function of the colours is still something of an enigma, as the beetle is nocturnal and is never usually exposed to sunlight.