Find a firefly phenomenon in the Great Smoky Mountains.

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.

The park in eastern Tennessee and western North Carolina is home to 19 species of fireflies, including 13 that flash. Only one — the synchronous firefly — turns the springtime mating ritual into an incandescent performance that dazzles like a laser show. After lying low in a larval and pupal state for one to two years, the freshly winged males rise from the forest floor and twinkle in concert. Apparently, girl fireflies are attracted to N’Sync sparkle.

“The males are saying, ‘Pick me,’ ” a park employee named John explained during a shuttle ride to the viewing site last week. “And the females are saying, ‘Beat it. I’m busy.’ They are looking for the brightest flash.”

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 midJune. 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, Tennessee, 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.

“This is their last hurrah,” John said. “It is a really cool way to go out.”

Spoiler alert: The adults die after mission accomplished.

The fireflies first attracted the attention of locals who lived in the park and vacationers who escaped the summer heat in mountain cabins. When the bulk of leases expired in 1991, the vegetation grew back, creating an ideal environment for the fireflies. In 1995, the National Park Service removed the streetlights; the darkness drew more fireflies to the area. In the following years, spectators would jam the small parking lot at Elkmont and crowd onto the Little River and Jakes Creek trails, treading heavily on the fireflies’ habitat. To control the madness, the park started managing the site. It closed the Elkmont lot and required guests to park at the Sugarlands Visitor Center and ride trolleys to the location seven miles away. It experimented with a first-come, first-served approach, which resulted in lines that rivaled opening night of “Star Wars: The Force Awakens.” Last year, the park instituted a lottery system, distributing 1,800 parking passes for vehicles holding up to six people. To determine the dates of the event, entomologist Becky Nichols relies on a formula that factors in the minimum and maximum air temperatures from March 1. She makes her prediction about eight weeks out. “I can get pretty close,” she said. This year, nearly 18,500 people applied for passes between April 25 and May 1. In addition, campers who reserve any of the 220 sites at the Elkmont campground can access the area by foot. The eight-night period started on May 30, and about 12,000 visitors experienced the “Fireflies Live!” show through its finale.

“You had a 7 percent chance of coming here tonight,” John said on the second evening. “Congratulations, you beat the odds!”

At 7 p.m. on Wednesday, the trolley line was several links long. It shimmied down one side of the lot, parted at the vehicle entryway, then resumed along the grass. People carried folding lawn chairs, blankets and coolers. Two kids played hacky sack with a set of keys. A college-age girl on a beach towel dealt UNO cards to her friends. Babies in strollers napped or looked wide-eyed at the incomprehensible scene.

I took my place behind a group of six adults, including an older gentleman with flowing white locks and Dickies overalls. A man passed around a tub of homemade brownies.

I wasn’t the caboose for very long; Mike Dean and Tanvia Kresse bumped me up to the penultimate position. During our slow march to the trolley, Mike told me he had unsuccessfully applied for a parking pass last year.

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“You just sit and wait on them,” advised the dad, Dickie.

Before entering the inky trail, park employees handed out squares of red cellophane and rubber bands, for covering flashlights and smartphones. Direct light can disturb the fireflies. You don’t want to be blamed for ruining the next generation, do you?

Visitors set up their gear — nice inflatable couch — along the ruddy path, which ended with a row of orange cones about three-quarters of a mile from the trail head. The scene resembled a parade route with people facing outward, at the thicket of tulip poplars, hemlocks, red oaks and maple trees. Pinpricks of red light appeared like beady mouse eyes in the woods, evidence of bushwhackers braving the poison ivy for a closer

look. When scouting out a viewing spot, Becky recommended a quiet area with an open understory and a dark canopy. Similar to a bar, the fireflies don’t want obstacles obstructing their communication channels. Instead of husky frat boys and pool tables, the insects have to contend with secondgrowth trees and boulders.

I walked a few steps in and saw a spark of light.

“One starts it, and then they all get going,” Becky said.

I had mistakenly assumed that the fireflies would switch on like floodlights at an evening baseball game, but the synchronicity was much subtler and less choreographed. For eight-to-10 seconds, pops of light swirled before me: high and low, to the left and to the right, in the foreground and in the background. And then, without warning, someone would pull the plug, and the fireflies would plunge into darkness.

During this seconds-long period, the females would respond with a double flash. However, their light was too faint to see, so I used my downtime to count Mississippis until the males resumed their courtship.

The moon was bright, and the fireflies weren’t as outgoing as the first night. (Becky expected them to peak on the fourth evening.) I discovered a pocket of activity halfway up the trail and watched transfixed. At 11, a park employee broke the magical spell. Time to catch the trolley.

I reconnected with the Hills on the return trek. The littlest member, Kennedy, was asleep in her grandfather’s arms. Her mother, Whitney Johnson, was stiff from carrying her, plus itchy from bugs. Her brother, Dustin, had to catch a 7 a.m. flight back to New York. They had a 90-minute drive ahead of them, and we didn’t board the trolley till close to midnight.

I asked the family if they planned to try for a third year of synchronous fireflies.

They all said yes.