Anecdotally I have seen a huge decrease in firefly's here in SE Michigan over the last few years. Five or so years ago you'd see hundreds of them while driving through the farm fields or sitting in your backyard enjoying a summer brewski. Last few years I hardly recall seeing any of them anywhere.
Same story in Ohio. Used to be able to drive along pastures and see thousands of fireflies.
My daughter saw some last night for the first time in quite a while. There were less than a dozen in a quarter acre area. She’s 19 and has noticed the difference.
(Same with Monarch butterflies albeit on a longer timescale)
I wonder if the many polar vortexes in 2014, (2015/2017?) have reduced insect populations substantially. I remember that foxes were frozen in fields in Columbus during 2014.
The polar vortex is a symptom of the weakening of the jetstream, thought to be occurring because of warming-driven melting of the arctic ice cap. Human-driven melting.
I didn't see them as much when I lived in a city, but I don't know how much of that was light pollution, it's very difficult where I am to get out someplace where you could see the Milky Way without a car, and when I would I'd see a lot but "swarm" isn't the word I'd use. More like pixels blinking in a weird pattern.
