How does a firefly make its own light?

A tiny light blinks above the grass, goes dark, then shines again. A firefly is flying there. It is a beetle with a light-making part near the end of its belly. That part is called a lantern, but it has no bulb or battery.

Inside the lantern, special body materials react with oxygen. A reaction changes materials and can release energy. In a firefly, some of that energy leaves as light. The beetle makes its own glow instead of reflecting light from the Moon or a streetlamp.

A flash can also carry a message. In many kinds of firefly, adults use light patterns to find a mate of the same kind. The spaces between flashes matter, rather like the pauses between sounds in a call. One firefly's flashing may receive an answer from another nearby.

Different kinds have different patterns, and some adult fireflies do not light up at all. A glowing firefly is doing two things at once: its body is making light through chemistry, and that light can help another animal find it in the dark.