Animal · United States, Canada
Firefly
Photinus pyralis — the name this animal has in the language scientists everywhere share.
The firefly is not a fly at all but a small beetle that makes its own light in the tip of its body and flashes it after dark. The common eastern firefly draws a short rising J of light every few seconds on warm summer evenings.
Picture credit: Celari817 (CC BY 4.0) · art farmer (CC BY-SA 2.0) · Wikimedia Commons
Where does the firefly live?
Home: Damp meadows, field edges and gardens in eastern America.
In the wild it lives in these countries: the United States, Canada.
Conservation status from the IUCN: not in danger.
The short profile
Fully grown: 9-19 mm long, about the size of a grain of rice. On the menu: meat.
The story behind it
The light comes from a chemical reaction in the last segments of the body, where a substance called luciferin reacts with oxygen and an enzyme called luciferase. Almost none of the energy is lost as heat, so the glow stays cold. Each species has its own signal. A male common eastern firefly flies his rising J every five to seven seconds, and a female sitting in the grass answers a second or two later with a single flash. On warm evenings the whole pattern speeds up, on cool ones it slows down. A firefly spends most of its life hidden in the soil as a larva, sometimes for two years, hunting snails, slugs and worms, and the glowing adult lives only a few weeks. Many adults never eat at all.
Find it on the globe
Firefly is there as a tiny animated figure that breathes and looks around. From far away the planet is only a blue ball; detail arrives as you zoom in, and this one appears once you are close enough. Open it on the globe.
It sits at its real coordinates, not near them — the same numbers listed in the facts above. Switch off the layer for this kind of place and it disappears again; the buttons for that are down the right-hand edge.
Questions children ask
Why do fireflies glow?
Mostly to find each other. Males flash a pattern while flying and females answer from the ground, so the two can meet in the dark without seeing anything else.
Is firefly light hot?
No, it is cold light. Almost all the energy of the reaction turns into light instead of heat, which is why a firefly can carry a lamp inside its own body without being burned.
What do fireflies eat?
The larva is a hunter and eats snails, slugs and worms in the soil. Most adults eat nothing at all and live for a few weeks on what they stored as larvae.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
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