Fireflies have special luminous cells, and there are two chemicals in the luminous cells, one is called fluorescein (firefly fluorescein in fireflies), and the other is called luciferase.

Fluorescein can consume ATP under the catalysis of luciferase and react with oxygen to produce stimulated oxidized fluorescein, which releases photons when it returns to the ground state.

Almost all the energy released in the reaction is released in the form of light, only a small part is released in the form of heat, and the reaction efficiency is 95%, so the beetle will not be overheated and burned. Humans have so far been unable to make such an efficient light source. There are many white patches on the lower abdomen of worms. In fact, it is the transparent part of the shell. There is a white film inside, which can reflect light. So this part looks white during the day.