In North America, there are more than 170 species of Lampyridae, or light-emitting beetles, and there are more than 2,000 types worldwide. And they've been around for millions of years.
, which is what firefly spotters likely see in backyards across the eastern half of the U.S. While they will avoid light where possible, they can tolerate it for a bit longer than most others.
This photo released by the Museum of Science shows a firefly or lightning bug. Fireflies are neither bugs nor flies; they are actually beetles, which have two pairs of wings. They loosen soil, which allows sunlight, oxygen and water to penetrate down below. The beetles also maintain a balance by eating slugs and snails, keeping those critters in check. And they serve an important role in the food chain themselves as grub for spiders and frogs, for example.