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This shiny beetle case is a surprising form of camouflage

When you think camouflage, you probably don’t imagine a gleaming turquoise bug that might be mistaken for a fancy brooch. But that’s the surprisingly perfect disguise for the jewel beetle (Sternocera aequisignata), researchers report today.

Scientists previously assumed that iridescent creatures such as dragonflies and some butterflies developed their majestic coloration to attract mates, or to warn predators not to eat them because they are poisonous. But a counterintuitive theory first proposed 100 years ago posits that iridescence might instead be a form of camouflage.

To find out, researchers filled nearly 900 jewel beetle wing cases, some naturally iridescent (above) and some painted with plain colors, with worms. They then placed them on plant leaves with different hues of green and glossiness at a nature reserve in the United Kingdom.

Birds were up to three times less likely to find worms in the iridescent wing cases than in the noniridescent ones, the team reports today in Current Biology. Humans had trouble, too: People in the park were up to six times less likely to find the iridescent wing cases than the plain ones—and the glossier the leaves, the harder the task.

The study is the first to show that iridescence can work as a form of camouflage, the researchers report. It could also explain why iridescence evolved to make many animals both disguisable and vibrantly colorful.