The lanterns on firefly butts consist of three layers, and the one in the middle produces light. The other two layers consist of microstructures that manipulate light in such a way as to increase transmission. The authors investigated this phenomenon more closely in the firely Pyrocoelia rufa. They began by using a scanning electron microscope to image the microstructures. The team found that these structures improved light transmission through various optical tricks, for instance by index matching and reducing internal reflection. Essentially, the firefly abdomen is a well-built organic light-emitting diode (OLED). Mimicking these structures, the researchers created their own OLED, roughly 35% to 61% brighter than normal OLED. http://acsh.org/news/2016/05/31/fireflies-inspire-brighter-leds/