Common eastern firefly

On warm summer evenings, you might see little lights blinking on and off above the grass, floating like tiny lanterns. Those lights come from the common eastern firefly. Even though it is called a fly, a firefly is really a small, soft beetle. It is one of the most common fireflies in North America, living across the eastern side of the continent from spring until early autumn.

A firefly makes its own light near the tip of its body, in a special glowing organ. Inside, a chemical mixes with air to create a cool, greenish-yellow glow that does not feel hot at all. This gentle light is the firefly’s way of talking. Each kind of firefly has its own blinking pattern, a little like a secret code made of flashes in the dark.

On summer nights, the flying males blink their light about every five to seven seconds as they drift through the air. A female resting on a leaf or a blade of grass watches for the right pattern, then flashes back to answer. By blinking to each other across the meadow, the fireflies find friends of exactly their own kind among all the twinkling lights.

Before they can fly and glow in the air, fireflies begin life as eggs, and even the eggs give off a faint light. The young that hatch are called glow-worms, and they glow too. These larvae live in damp soil, under bark, and near streams, where they hunt for small worms, slugs, and snails. A firefly may spend a long time as a larva, sometimes as long as two years.

Grown-up fireflies live for only a few short weeks, and many of them eat little or nothing during that time. They spend their brief adult lives lighting up the evening and looking for a mate. Fireflies need damp ground for their glowing young and meadow or woodland edges for the adults. Leaving moist leaf litter and a little wild grass helps keep summer evenings friendly for these gentle beetles.