The History of An Orange Glow

The glow of a beetle has inspired an elegant bit of evolutionary detective work that appears in the Proceedings of the National Academy of Sciences. Americans like myself are familiar with fireflies, but in the tropics the night is also illuminated by beetles. When Darwin came to Brazil on the Beagle, he amused himself by noting how the beetles were "rendered more brilliant by irritation." Naturalists have gotten a bit more sophisticated at studying beetles since then. They now know that the male beetles use the light organs on their underside to get the attention of females that are sitting in the trees and bushes; when the female sees a glow she likes, she registers her approval by flashing light organs on her back. (Fireflies do the same thing, but while they flash, the beetles give off a steady glow.) Scientists also know how the glow is made--a gene creates ...