Why do Fireflies Glow?

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Jim Gilbert

Front yard, Bernardsville, NJ

Fireflies. Most of us know them as the friendly, glowing little creatures that greet us during the summer months, but do we know why or how they light up the night? In other words, why, and how, do fireflies glow? The answers to these questions, and more, are as follows…

To begin with, why do fireflies glow? According to an article written on www.scientificamerican.com, “Fireflies appear to light up for a variety of reasons… [they] produce defensive steroids in their bodies that make them unpalatable to predators. Larvae use their glows as warning displays to communicate their distastefulness.” The article continues, stating that “As adults, many fireflies have flash patterns unique to their species and use them to identify other members of their species as well as to discriminate between members of the opposite sex…The adult fireflies of some species are not luminous at all, however, and instead use pheromones to locate mates.”

Additionally, how exactly do they do it? How do fireflies glow? An article on livescience.com answers this question, stating that “The light is a result of the mixing of oxygen, a pigment called luciferin, the enzyme luciferase,[and] a chemical called adenosine triphosphate (ATP), which provides cells with energy…Uric acid crystals, located in the cells that are activated to make the light, act as a reflective layer and shine the light away from the bug’s body.”

So, more or less, why and how do fireflies glow? It all comes down to science.