Synchronous fireflies: In a dark forest, tiny creatures flash in unison and light up the nightBy BETH J. HARPAZ and TED ANTHONYJune 20, 2018 GMTIt's not unusual to see fireflies flashing in backyards here and there this time of year. But deep in a Pennsylvania forest, synchronous fireflies blink in unison in a rhythmic display that lights up the night.