What is the purpose of a lighting-bug?

Question

What is the purpose of a lighting-bug?

Answer 1

if you're asking why they flash, or light up, it's because they're trying to find a mate.

Answer 2

They are good to have in the garden. They can be found in dark and moist areas in the garden where the larvae prey on terrestrial snails and slugs.

It is interesting to note that the enzyme (luciferase) that is used by lightning bugs to create the light is found to have medical benefits to humans and is being tested for certain cancer fighting qualities.