> We live rural southern Ontario and fireflies are usually just a single weekend or so at the end of June or beginning of July. But this year they went on for almost two months. They only just stopped about a week ago.

I wonder if this is cyclical behavior. We had a year like that last year down in NJ. This year it was back to maybe only a week. I live in the west part of the state surrounded by parkland. Rainfall was the only thing that was dramatically different this year. Last year was extremely wet spring and early summer (when they appeared) followed by an extremely dry end of summer into fall. This year we've had average rain in almost every month. The rain evidence isn't anecdotal, I have a state rainfall gauge a couple miles down the road from me with records going back at least a few decades.