Growing up, I loved catching fireflies (or lightning bugs). Truth be told, I still do. What’s not to like about a bug whose rear end glows on command? And scientists just gave me a new reason to appreciate these remarkable creatures: some scientists have gained inspiration for an energy-conserving idea by understanding how fireflies work.
Energy conservation almost always brings good benefits. Better lights and more efficient appliances reduce my electric bill and also ease the strain on the power grid. Although fireflies emit a relatively small amount of light, they generate and project that light with a stunning efficiency. A standard incandescent light bulb has an efficiency around 10 percent. Consequently, the bulb wastes 90 percent of the energy coursing through it as heat. That’s why you don’t want to touch an incandescent bulb with the switch on. LEDs and fluorescent bulbs emit a much higher amount of light, with an efficiency between 40 and 90 percent. In contrast, fireflies emit light with almost 100 percent efficiency! Aside from requiring a minimal amount of energy, this means that the firefly doesn’t have to worry about dissipating wasted heat, especially on hot summer nights.
Image 1: Firefly in Hand
I found it remarkably hard to photograph a lit firefly, especially with a photobombing dog in the background!
Recent work identified an important mechanism that allows fireflies to transmit that light from their bodies into the air. Since the light generation occurs inside the firefly’s cells (with a high index of refraction) and the light must then pass into air (with a low index of refraction), the process of total internal reflection would reduce the amount of light escaping a firefly’s body.
However, the scales covering the firefly’s abdomen mitigate the problem by producing an “abrupt roughness in air,” thus causing a “lowering of the refractive index at the level of the cluster of photocytes, where the bioluminescent production takes place.”1 In other words, the mechanical structure and arrangement of the scales provide an abdomen-to-air transition that minimizes losses from total internal reflection. Engineers then mimicked this system to increase LED efficiency by 55 percent!
The lead scientist summarized the work by noting that