'Magical' lightning bug show expected soon at Congaree National Park

With the weather warming, rangers at Congaree National Park are preparing for what is becoming the preserve’s single biggest annual event: the return of synchronized fireflies.

The firefly spectacle brings crowds to the park because it so unusual. For about two weeks each spring, hordes of fireflies light up in unison, rather than twinkle individually as they would at other times of the year.

This spring, the park is, for the first time, using a forecasting method to predict when the fireflies will start blinking together. The method relies on a computer to crunch temperature data, because sustained warm weather is thought to trigger the coordinated flashing.

According to the latest computer run, it looks like May 20 will be the earliest date the firefly show breaks out in full force, park ranger David Shelley said. The fireflies should display their synchronized blinking until early June, before their lights again become sporadic, park officials say.

“The experience is absolutely magical,’’ Shelley said of the lightning bug show. “As a park ranger and a scientist, I get goosebumps when I stand out there and see these fireflies.’’

Synchronized fireflies light up in a handful of other areas around the country, including the Great Smoky Mountains National Park in Tennessee, a spot in Pennsylvania and another site in Tennessee.

But the synchronized blinking, thought to be part of a firefly mating ritual, is a rare occurrence, experts say.

In Columbia, the bugs have been lighting in unison for years. However, people started to find out about their shows only recently, pouring into the park.

Last year, as many as 4,000 people visited Congaree to see the lightning bugs. That’s about a fourth of the people who came to the park for the entire month of May 2017, park ranger Jon Manchester said.

Some people complained the crowds were uncontrolled, taking away from the experience last year. So, this year, the park has extended the hours that park rangers will be on duty. Rangers also are offering an array of tips for seeing the firefly show.

John Grego, who heads Friends of Congaree Swamp, said the synchronized fireflies “have increased the park’s visibility. Certainly the big trees, the quiet and the water bring people in year-round. But this is another experience that has really connected with the public.’’

One of the best places to see the fireflies is along a hill near the visitor’s center, where the bugs congregate. A new twist this year is the creation of a "firefly trail,'' a path that winds its way through the bottom land forest near the visitor's center.

There are as many as 2,000 species of fireflies, which often thrive in humid moist areas of Asia and the Americas, according to National Geographic. The paper-clip sized bugs, cousins of beetles, have organs under their bellies that light up when the insects take in oxygen. Each species has a unique light pattern that helps them find mates, National Geographic reports.

While the fireflies at Congaree National have put on quite a show in recent years, the number of fireflies, in general, is thought to be dwindling worldwide because of habitat loss, pesticide exposure and light pollution from cities. Several years ago, Clemson University launched a project to determine if fireflies are less abundant than in years past.

The sensitivity of fireflies is one reason Congaree National is asking visitors to limit the use of flashlights and avoid spraying mosquito repellant while in the park. The park also is advising visitors not to set up folding chairs. At the same time, walking outside the firefly trail or other park paths could destroy lightning bug nests filled with females and larvae, park officials said.

“The females are in the ground, in the leaf litter on the edge of the trails,'' Shelley said. "So we don’t want to trample their habitat. If there were issues with females, in future years, there might not be fireflies to see.’’

▪ For more information about this year’s synchronized firefly spectacle, see Congaree National Park’s website. Park officials say they will keep the web page updated for the latest on the expected return of the synchronized blinking.

Firefly watching advice, rules

Some tips for viewing the fireflies at Congaree National Park

▪ Optimum viewing time is shortly after dark until about 10 p.m.

▪ Be prepared to walk the firefly trail; the boardwalk will be open only to those with mobility issues.

▪ Stay on designated paths; otherwise, you risk trampling firefly nests.

▪ Do not use flash photography, and limit use of flashlights.

▪ Carpool when possible because of limited parking.

▪ Do not catch fireflies in jars or other containers.

This story was originally published May 10, 2018 at 7:19 PM with the headline "'Magical' lightning bug show expected soon at Congaree National Park."