I have plenty of fireflies. I also don't leave my porch light on all night. Light pollution is causing a decline in fireflies, too. I have my mower set at the highest setting 3 1/2". I do not mow every week and don't mow some areas at all. I have a 6' fence so the backyard isn't totally visible.
Herndon, VA (USA)
Take care of the small things....