In a limited engagement, the fireflies blink in sync in the Great Smoky Mountains (WaPo)

By Andrea Sachs June 7

It starts with a flicker of light. Two, three, four flashes follow. Minutes later, dozens of tiny yellow bulbs illuminate the forest like paparazzi hounding the Keebler elves. And then the woods go black. Show’s over — at least for the next eight-to-10 seconds.

For two or three weeks in late May and early June, Great Smoky Mountains National Park pulsates with light and darkness, the beginning and end of life, and Photinus carolinus and Homo sapiens.

“Every year, I think I am prepared and then I get blown away by it,” said Dana Soehn, a public affairs specialist at the national park, who has witnessed the natural phenomenon numerous times.
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Synchronous fireflies are uncommon: Only three species inhabit North America and most live in the Appalachian regions stretching from Georgia to southern Pennsylvania. Congaree National Park in South Carolina typically welcomes Photuris frontalis for two weeks between mid-May and mid-June. This year, the viewing season wrapped up on May 27, several days before the arrival of the Smokies population.

Great Smoky rangers have spotted the insects throughout the 522,427-acre park, but the Elkmont section near Gatlinburg, Tenn., contains the largest concentration of synchronous fireflies. When the conditions are ripe for romance — no rain, dark skies, kill the moonlight — thousands of the fireflies will flirt on a verdant tract of land laced with hardwood trees and a burbling river.
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more: https://www.washingtonpost.com/lifestyle/travel/in-a-limited-engagement-the-fireflies-blink-in-sync-in-the-great-smoky-mountains/2017/06/06/c5aa2004-4a0b-11e7-bc1b-fddbd8359dee_story.html