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We Now Know Why These Beetles Are so Dang Beautiful

They’re jewel (scarabs) in the rough.

by Samantha Cole
Jun 19 2017, 10:00am

Image: Wikimedia Commons

When it comes to aesthetics, most beetles aren't exactly worship-worthy. Even iridescent June bugs blend in with their green and brown surroundings, and most brightly-colored scarabs stick to natural tones in green or blue.

The Central American Chrysina resplendens, however, is fancy as hell. Also known as a jewel scarab, this beetle's survival tactic is to wow the heck out of its predators with its beautiful golden exoskeleton. It looks like something plucked from Aladdin's cave of wonders, but until recently no one could explain its distinctive golden sheen.

To find out what makes these scarabs glow more than most, physicists at the University of Exeter mapped the optical signature of the beetle's exoskeleton using transmission electron microscopy, an imaging technique that maps objects by bombarding them with negatively charged particles. The researchers found that that the scarabs' color is due to nano-structures that manipulate light. As light travels along the scarab's back, it hits the nanostructures in repeating, varying layers. A range of visible colors is reflected simultaneously, producing that metallic golden hue.

Looking like a bright golden spot of sunshine in the forest floor might seem counter-intuitive to not getting eaten, but the researchers suspect that it's a less dull approach to camouflage and defense.

"The shiny golden colour could also change how the beetle is seen as it moves, potentially dazzling a would-be predator," Dr. Martin Stevens, associate professor of Sensory and Evolutionary Ecology at the University of Exeter said. "There are many species which are iridescent but jewel beetles are one of the most charismatic and brightly coloured, and their colour might be used in mating."