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Jewel beetles are pretty eye-catching with their glossy, bright coloration. But if you were a small creature that needed to avoid predators, you might think that eye-catching is the last thing you'd want to be. But it turns out that their iridescence doesn’t hinder their camouflage...it IS their camouflage!

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Sources:
https://www.cell.com/current-biology/fulltext/S0960-9822(19)31608-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982219316082%3Fshowall%3Dtrue
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2706478/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2586663/
https://academic.oup.com/beheco/article/18/6/1123/211740
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424625/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5970230/

Images:
https://www.istockphoto.com/photo/image-of-green-legged-metallic-beetle-or-jewel-beetle-or-metallic-wood-boring-beetle-gm1176768288-328240101
https://commons.wikimedia.org/wiki/File:Rainbow_boa_peruvian.jpg
https://commons.wikimedia.org/wiki/File:Haliotis_iris_LC0283.jpg
https://www.istockphoto.com/photo/jewel-beetles-gm1226562238-361432452
https://www.eurekalert.org/multimedia/pub/221783.php?from=452853
https://www.eurekalert.org/multimedia/pub/221907.php
https://www.istockphoto.com/photo/pastel-colored-holographic-background-gm1136408675-302643224
Thanks to Brilliant for supporting this episode of SciShow.

Go to Brilliant.org/SciShow to check out their course on Waves and Light. [♩INTRO]. Iridescence is the seemingly magical ability of a surface to change color, depending on the angle you view it from.

It's found all over the animal world, but some of the most spectacular iridescence is found on the backs of jewel beetles. But these beetles aren't bright and shiny to show off. Strange as it may seem, there's evidence that they're using their coloration… to hide.

Most colors we see around us are produced by pigments, chemicals that absorb certain wavelengths of light and not others. But iridescence is different. It's a structural color, which results from light interacting with the microscopic physical structure of a surface.

And it's responsible for some of the most brilliant colors in nature. These jewel beetles produce their iridescence using a multilayer reflector, which is a stack of thin layers of a molecule called chitin. As light reflects off each of these layers, the reflected waves are scattered to produce many different colors.

And the angles are all a little different too, so look from one angle and you see blue, but tilt your head a little and now it's green. Now, eye-catching colors don't seem like they'd be an advantage to an animal that's so often prey for birds. But in February 2020, a team of researchers published a study in the journal.

Current Biology showing that it might not be so eye-catching after all. They made 900 model beetles in different colors. Some were iridescent, some were solidly colored, and some were painted with a rainbow that looked like the iridescent pattern, but didn't change when looked at from different angles.

They filled each model beetle with mealworms as a tasty treat for hungry birds and placed them on leaves throughout a forest. After two days, they counted how many of each color had been eaten, and found that iridescent and black beetles survived better than any of the other colors. They came up with two hypotheses to explain this.

One, the iridescence was acting as a warning sign to predators the way poisonous animals are sometimes brightly colored. Or two, the predators had a harder time seeing the iridescent beetles, because they were better camouflaged. Unfortunately it's difficult to interview birds about their diet choices, so they got a few dozen humans together and organized an Easter egg hunt for beetles.

Since people don't usually eat mealworm-stuffed model beetles, warning signs or food preferences didn't matter. The experiment only tested the effect of camouflage. And the results were similar.

The iridescent and black beetles were the best hidden. There aren't any iridescent forests for beetles to blend into, but there are lots of shiny leaves. In this study, if an iridescent beetle sat on a glossier leaf, it had less of a chance of being spotted.

The model beetles with the rainbow pattern on them were found easily, so it's not just having many colors, it's that they change when either the beetle or the predator moves. This is called dynamic disruptive camouflage. By constantly changing, the colors confuse the predator's mind, never giving them a clear outline of the beetle to focus on.

Other studies have found bees have a harder time recognizing iridescent shapes and birds need more attempts to catch iridescent targets. So next time you're searching for a beetle, or an Easter egg, remember that nature sometimes has a way of hiding in plain sight! If you're fascinated by the way these beetles use light to create brilliant shifting colors, you might like the course Waves and Light over on Brilliant.

It'll teach you all about light, not to mention other stuff that travels in waves, like sound. Brilliant is an online learning platform that aims to help you sharpen your math and science skills. The interactive elements in each course are designed to keep you engaged and help you hone your thinking skills.

Courses are even available offline via their iOS and Android apps, so you can keep learning even when the Internet's spotty. Best of all, the first 200 people to sign up at Brilliant.org/SciShow will get 20% off an annual subscription to Brilliant Premium. You can head over there to learn more. [♩OUTRO].