Beetle Uses ‘Switchable Reflector’ To Change From Gold to Red

Beetle belongs to the Cassidinae family. Charidotella sexpunctata - Golden Tortoise Beetle. Wikimedia commons: Ilona Loser

The Panamanian golden tortoise beetle (Charidotella egregia) has developed a way to change color via liquid channels. The method in which these beetles alter their hue is “something very rare,” says lead author Jean Pol Vigneron of the University of Namur in Belgium in a Science News article. The paper was published in Physical Review E (2007).

The beetles can be found munching on the morning glories of Cerro Galera, six kilometers west of Panama City. Normally they have a metallic sheen, but if disturbed they will shift to red in under two minutes.

​Their ability to adjust the reflectivity of their shell is very different from other animals—such as chameleons and squid—that change color via expanding and contracting pigment cells in their skin. Their exoskeleton acts as a sort of portable mirror using liquid, changing color via nano-sized channels that control fluid levels in the layers under their shell. When moisture fills these channels, the layers of the shell become smooth and evenly reflect light for a mirrored effect. When stressed, the beetle dries up that fluid, diminishing the mirror-like properties and revealing the base red pigment beneath. The researchers liken this ability to “a switchable reflector.”

According to Vigneron, this novel mechanism could be used to improve upon optical vapor sensors in detonating environments where, for instance, the use of classic electric probes would be too hazardous. 

Image Credit: Jean Pol Vigneron and colleagues, Physical Review E 76, 031907 (2007)

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