Why Do Fireflies Light Up?

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Photo via Fiona M. Donnelly in Smiths Falls, Ontario.


Story by EarthSky.
Fireflies are sometimes called lightning bugs. Many a child has spent a summer evening chasing them. And maybe you’ve wondered – how and why are these insects able to light up? The answer is that the light of a firefly is a chemical reaction, caused by an organic compound in their abdomens. The compound is called luciferin. As air rushes into a firefly’s abdomen, it reacts with the luciferin, and a chemical reaction gives off the firefly’s familiar glow. This light is sometimes called “cold light” because it generates so little heat. The firefly can regulate the airflow into the abdomen to create a pulsating pattern.

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“Fireflies on top of the wave of grass and overflowing. Biggest firefly show in years.” by Eileen Claffey in West Brookfield, Massachusetts, June, 2015.

Some experts think the firefly’s flashy style may warn predators of the insect’s bitter taste. On the other hand, some frogs don’t seem to mind. They eat so many fireflies that they themselves begin to glow. Male fireflies also light up to signal their desire for mates – and willing females attract the males with flashes of their own. But not all the flashing of fireflies is motivated by romance. While each firefly species has its own pattern of flashing, some females imitate the patterns of other species. Males land next to them – only to be eaten alive. So the next time you see a firefly, keep in mind that its flickering isn’t just a wonder of the night. It’s also a unique love language … that can be deadly.

 

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