The field behind my previous home in NY State had so many fireflies on those "special nights" when the temperature and humidity were just right, that it looked like blue-green ocean waves of constant but twinkling light all the way across the field. We frequently watched them from the fence line until the early hours of morning. Of course, my kids had to capture as many as possible and put them in jars, but I made them release all of them the next night. I explained to the kids that one night was OK, but keeping them longer would kill them, and once released, they could capture new ones for an over night stay in the jar the next night. It went well, and helped teach them an appreciation of the wild. Here, we have them on the lawn between the house and the lake, but their numbers are less than about 10% of what existed in that field in NY State.
Charley