The brilliant metallic iridescence of so-called jewel beetles, such as the Chrysina gloriosa seen here, arises not from chemical pigments but from the physical structure of the beetles’ exoskeleton. The beetles share that morphological trait with several other creatures, including butterflies, birds, and fish (see Physics Today, October 2006, page 82). But as Albert Michelson observed almost a century ago, the light reflected off certain beetles is circularly polarized. New work by Mohan Srinivasarao and colleagues at Georgia Tech has linked the left-handed iridescence of C. gloriosa to intriguing similarities between its exoskeleton and a certain kind of liquid crystal.
Viewed under a microscope, the exoskeleton contains cells—mostly hexagons, plus some pentagons and heptagons—that are about 10 µm across and appear green with a yellow core. Confocal microscopy revealed more detailed information: Each cell has a shallow, central, conical peak surrounded by nested arcs. That topology closely resembles...
