Fireflies are soft beetles that belong to the family Lampiridae. There are over 2,000 species around the world and they’re found everywhere except Antarctica. Fireflies (also called lightning bugs) have a special protein in their bellies, a pigment called luciferin. As the insect breathes, air rushes into tubes in abdomen where oxygen reacts with the luciferin. The chemical reaction gives of the glow with which we’re so familiar.