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Thousands of Fireflies Will Create a Spectacular Light Show in the Great Smoky Mountains

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Synchronous fireflies are a unique species that actually synchronize their light display.

Photo by WUT.ANUNAI/Shutterstock

Synchronous fireflies are a unique species that actually synchronize their light display.

Each year, countless lightning bugs converge upon the national park, flickering among the trees in one of the country’s most beautiful forests. Details regarding how to get access (a limited number of people can attend) have just been released.

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The Great Smoky Mountains National Park is gearing up for its annual synchronous fireflies event, during which swarms of lightning bugs will light up the park at night. The once-a-year phenomenon is so popular that a lottery system has been established for obtaining the coveted parking passes required to attend.

This year, the lottery for the parking passes to see the fireflies opened on April 27, 2021, at 10 a.m. EST and will close on May 3, 2021, at 11:59 p.m. EST. You can enter the lottery at Recreation.gov. The event will run from Tuesday, June 1, through Tuesday, June 8, 2021.

Due to the COVID-19 pandemic, the viewing opportunity has been modified for safety, and during the peak firefly display period, there will not be a shuttle service from the Sugarlands Visitor Center as in years past. For $24 per vehicle (seven passengers maximum), successful lottery applicants will automatically obtain the vehicle pass necessary to access the Elkmont viewing area, where the largest gathering of synchronous fireflies in the Western Hemisphere occurs. After checking in near the Elkmont Campground Kiosk, parking attendants will direct vehicles into designated parking areas, where visitors can then exit their vehicles for viewing. A designated number of ADA parking spaces will be available on a first-come, first-served basis.

The firefly display takes place in the Elkmont section of the Great Smoky Mountains National Park.


So, what are synchronous fireflies, exactly? They are a unique species of firefly (a type of beetle also known as a lightning bug) that can actually synchronize their flashing light displays. Their light patterns, which are produced in their “lanterns” along their abdomens, are part of a mating ritual that helps males and females recognize each other. The males will fly and flash their light and the typically stationary females will respond with a flash, according to the park’s dedicated synchronous fireflies page

No one is exactly sure why the fireflies flash their lights in unison, and they don’t always do so. When they do, a burst of light ends with an abrupt period of darkness.

Fireflies’ bioluminescent lanterns are tucked into their abdomens.
The peak mating season lasts for approximately two weeks each year, and the dates of the display vary from one year to the next. Scientists predict the dates based on factors such as temperature and the moisture in the soil. Even during the peak season, attendees aren’t guaranteed a perfect display, the park has cautioned. Environmental factors such as rainfall or cooler temperatures that fall below 50 degrees can shut down the display on any given night.

Nevertheless, those who would like to try their luck at having the rare chance to see the annual phenomenon will need to enter the online lottery by May 3. A total of 800 vehicle passes will be distributed for the eight-day event (or 100 per day), with no vehicle to exceed seven passengers.

Lottery applicants will be informed via email on Friday, May 7, about whether they have successfully obtained a vehicle pass. Each pass is valid only for a specified date, and an arrival time between 6:00 p.m. and 8:00 p.m. will be assigned. Lottery winners will automatically be charged a $1 application fee and $24 vehicle fee. No additional passes beyond those assigned during the lottery will be made available.


Attendees are asked to cover their flashlights with red or blue cellophane so that they don’t disrupt the viewing experience and to turn them off altogether when they have found a viewing spot. They are also asked to stay on designated trails or paved surfaces at all times, and to not catch the fireflies, so leave those Ball jars at home, folks!

This article originally appeared online in April 2019; it was most recently updated on May 3, 2021, to include current information.

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