Sparkly exoskeletons may help camouflage beetles from predators
Iridescence sparkles across many branches of the tree of life, from dazzling ruby-throated hummingbirds to bright, metallic beetles. While ostentatious coloration can woo mates, scientists had assumed it also attracted predators. But new evidence suggests an unexpected benefit of iridescence — camouflage. Asian jewel beetles (Sternocera aequisignata) boast brilliantly iridescent exoskeletons, and the fact that both males and females share this trait suggests its importance outside of mating. To see if iridescence affected whether beetles were detected by hungry birds, behavior ecologist Karin Kjernsmo at the University of Bristol in England and colleagues pinned mealworm-stuffed iridescent beetle wing cases to forest leaves along with non-iridescent ones artificially colored blue, green, purple, rainbow or black. All 886 targets — iridescent and matte — represented the spectrum of colors in the iridescent shell, allowing researchers to disentangle the effects of individual colors from the ever-changing sparkle of iridescence. Wing cases of the Asian jewel beetle tilted different ways show the diversity of colors iridescence can produce. Most...