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Question: How do fireflies create bioluminescence?
It's interesting that so many people were enamored with the fictional bioluminescent life of the movie "Avatar" (me too) when we have so much wonderful life actually on our own planet Earth. Some take it for granted that fireflies light up the night, but it's truly amazing to think about the fact that we have insects that produce flashing light in aerial displays. Fireflies are one of the highlights of natural displays in summer.
Despite their common names of fireflies or lightning bugs, fireflies are neither flies nor true bugs. Fireflies are actually a Coleopteran beetle in the appropriately named family "Lampyridae." Perhaps we should call them firebeetles? Their flashing light display is produced when a type of chemical called luciferin reacts with oxygen and releases energy. The chemical reaction is catalyzed (sped up or started) by an enzyme called luciferase. It seems simple, but it is a truly amazing form of "cold light." The reaction is very efficient in that it produces little heat. In fact, over 90% of the energy released is in the form of light which is a good thing since too much heat from the reaction would likely hurt the firefly. Compare this with the average light bulb which releases only 10% of its energy as light and the rest is released as mostly heat which is why we shouldn't handle a lit bulb with bare hands.
Scientists don't yet know exactly how the flashing is controlled. It could be nerves signaling the release of certain molecules or the amount of oxygen allowed into the light producing organ of the abdomen of the firefly. To make things more complicated, the reason for lighting the night and even the color is different depending on the age and species of the firefly. As adults, different species have different flashing patterns of yellow or green in order to attract mates of their own species. There is at least one species of firefly which exploits the courting display to mimic other species and eat them! Several species don't flash as adults. The larvae of fireflies also produce light, but it is for a very different function. Firefly larvae taste bad and they tell predators not to eat them by glowing blue.
In addition to the 2000 species of fireflies, several other types of organisms include species that bioluminesce using some variations of light producing chemicals. There are glowing microbes, mushrooms, fish, and deep sea creatures. Some glowing organisms, certain species of fish, don't actually produce their own light, but incorporate bioluminescent microbes into special organs on their bodies. Bioluminescence is a fascinating way to look at the diversity of life with which we share our planet.
The Museum of Science, Boston is monitoring firefly activity with a citizen interactive Firefly Watch program at https://www.mos.org/fireflywatch/
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