Slowly going away. I remember, when I was a kid, out during the summer in the backyard. You would see so many of these little fuckers in every direction you look. Just all over the place. Now, during the summer, you are lucky to see one every few minutes.
Where I live they seem to come and go. Some years there's literally zero, then a few years later there'll be so many you almost don't wanna go outside because they might get in your mouth. Although admittedly I haven't seen the usual swarms lately either. It's long overdue and yet they're not here.
It's a big change from when I was a kid, still living in this same area, but we had a consistent, manageable number of fireflies every year.