Sunday , February 28 2021

Jewel beetle's bright colored shell serves as camouflage from predators – Ars Technica, Ars Technica

    

      Shiny things –

             

University of Bristol scientists offer first real evidence for a – year-old theory.

      

           – Jan , (4:) PM UTC            

( the brightly colored shell of this jewel beetle is a surprisingly effective form of camouflage, according to a new study by scientists at the University of Bristol. Artist and naturalist The brightly colored shell of this jewel beetle is a surprisingly effective form of camouflage, according to a new study by scientists at the University of Bristol. Abbott Handerson Thayer became known as the “father of camouflage” with the publication in of a book on coloration in animals. He was particularly fascinated by the phenomenon of iridescence : many species exhibit bright, metallic jewel tones that shift hues depending on viewing angle. While iridescence is often viewed as a means of sexual selection — think the magnificent peacock, shimmering his feathers to attract a willing peahen — Thayer suggested that in some species, it was also an effective means of camouflage.
Thayer endured a fair bit of mockery for his ideas, most notably from Theodore Roosevelt , a big game hunter who thought Thayer had grossly overstated his case. Indeed, there have been very little empirical support for Thayer’s hypothesis in the ensuing century. But researchers from the University of Bristol have now uncovered the first solid evidence for this in the jewel beetle, according to a new paper in Current Biology.
What makes iridescence in nature so unusual is the fact that the color we see does not come from actual pigment molecules, but from the precise lattice-like structure of the wings (or abalone shells, or peacock feathers , or opals , for that matter). That structure forces each light wave passing through to interfere with itself, so it can propagate only in certain directions and at certain frequencies. In essence, the structure acts like naturally occurring diffraction gratings. Physicists call these structures photonic crystals , an example of so-called “ photonic band gap materials, “meaning they block out certain frequencies of light and let through others.

Enlarge / The angle-dependent change in colors of the iridescent jewel beetle’s wing case . Karin Kjernsmo It has only been in the last few years that the first bits of evidence for iridescence as camouflage have emerged. In , Thomas Pike of the University of Exeter reported that iridescence seemed to interfere with birds’ ability to capture simulated virtual prey. And in a paper , Karin Kjernsmo, an evolutionary and behavior ecologist at the university of Bristol, and several colleagues showed that it also made it more difficult for bumblebees to identify a target shape. They connected “that iridescence produces visual signals that can confuse potential predators, and this might explain the high frequency of iridescence in many animal taxa.”

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