Ultra-thin Beetle Scales Are Whiter, Brighter, Through Light Scattering Surface

The bright whiteness of the Cyphochilus beetle is unusual in nature. [Image courtesy of P. Vukusic-University of Exeter]

The ultra-thin white scales of the Cyphochilus beetle—brighter than milk, tooth enamel or most other white materials found in nature—have an extraordinary light-scattering structure, according to a new Brevium in the 19 January issue Science.

Unlike other colors, whiteness is relatively uncommon in animals, since the surface substance must be able to scatter all visible wavelengths of light in order to appear white.

In their article, Pete Vukusic and colleagues in the United Kingdom describe the flat, overlapping white scales—many times thinner than most white synthetic materials—covering the beetle's body, head and legs.

At 1/200 mm thick, about 10 times thinner than a human hair, the scales were analyzed by mounting them upon needle tips and directing light to the center of the scales. The scientists then imaged and analyzed the reflection and diffraction patterns on a spherical screen.

"Their scales are characterized by their exceptional whiteness, their perceived brightness, and their optical brilliance, but they are only 5µm thick," the authors write. "This thickness is at least two orders of magnitude thinner than common synthetic systems designed for equivalent-equality whiteness."

The researchers hypothesize that the beetle's whiteness evolved as a camouflage to mimic a white fungus, indigenous to Southeast Asia.

Kathy Wren

18 January 2007