Years back I moved to the Prairies in a very small village for a number of years. I didn't like it but that's not the point. The first year I was there, in the evenings before dark, I saw a few fireflies and I was so excited! I had lived west of the Rockies and moved back here. There are no fireflies who light up west of the Rockies in all of North America. I only saw the fireflies for two evenings and no more.
With the heavy use of herbicides and pesticides plus regular crop dusting, I think they were wiped out by everything the farmers used. They had a cavalier attitude to using chemicals like this. I overheard one farmer's wife telling another that she always treats her vegetable garden with Round-up before she plants. Claimed it does wonders in controlling the weeds. 😵