What organic compound causes fireflies to light up?

Where did the fire flys go? When I was a kid in the 1960’s there were so many. The night sky’s were full of them. Now you rarely see them. I

Daybonn, Exactly, when I was a kid I could literally fill a jar with them.

And of course Lucifer’s name means bringer of light, and lux, luz, all mean light so the etymology is obvious.

My favorite part is that sometimes some of the frogs that eat them start to glow too. SO Freaking Cool 😎

Daybonn, Ten years ago or so, I saw thousands of lightning bugs on the edge of a field and forest lighting up the early night sky. There were so many of them it looked like Fairy Dust!

I still see a lot of fireflies. I have heard they need clean water to reproduce.

Daybonn, same with what we call Christmas beetles. Here, I think it is solely due to urban encroachment.SAD

guessed right, unbelievable!!!