A firefly sits on a leaf in Belize's Cockscomb jaguar reserve.
You can see the pale yellow light-emitting organ at the back of its body, which combines an enzyme called luciferase with pigments called luciferins in the presence of oxygen and ATP to create a flashing yellow light. Unlike human lightbulbs, this is a cold light without any infrared or ultraviolet wavelengths.
There are over 2000 species of firefly scattered around the world, but despite their name they're beetles and not flies. Fireflies are not the only type of beetle which emit light, some net-winged beetle larvae also do this trick, and this species of firefly shares its forest with a bioluminescent click beetle.
Photograph by Richard Seaman
Click here to comment on this picture.