Synchronous Fireflies

Great Smoky Mountains National Park has had the market cornered on synchronous fireflies for years. But thanks to a relatively recent discovery, the Blue Ridge Mountains just might give it a run for its money.


The Photinus carolinus is a species of firefly that each year, typically in the spring, put on a synchronous light display in order to find a mate. They are the only species in America whose individuals can synchronize their flashing light patterns.

CREDIT: JIM MAGRUDER

For decades, it was believed that the Smokies had the only population of synchronous fireflies in U.S. And while synchronous fireflies were eventually identified in Pennsylvania, South Carolina, and in two other parts of Tennessee, the Smokies have always gotten the glory. In fact, the annual viewing event at the Elkmont Campground in Gatlinburg, Tennessee, is so popular that the National Park Service instituted a lottery system for tickets.

So, you can imagine how surprised Dr. Clyde Sorenson, a professor of entomology at N.C. State University, was by what he saw when he spent the night on Grandfather Mountain in June 2019.

"I noticed them immediately by their flash pattern—they were synchronous. By 10 p.m. there were hundreds of them. I walked up and down the roads and they were all through the woods. It thrilled me to death," Sorenson told the Asheville Citizen-Times.  TO READ MORE ABOUT THESE FIREFLIES, CLICK HERE...

Fireflies Sync Their Flashes

Swarms of synchronous fireflies are rather like melting ice, or at least that’s how Raphael Sarfati, a physicist, sees it. Ice remains solid until it warms to a certain temperature and becomes a liquid. Likewise, a loose swarm fireflies will flash the lanterns in their abdomens randomly. But when the swarm reaches a certain density, the fireflies begin to blink in unison.

“Above that threshold, it is almost perfect synchronization,” with rhythmic, coordinated waves of light, said Sarfati, a postdoctoral associate at the University of Colorado, Boulder.

The spontaneous synchronization of certain species of fireflies, such as Photinus carolinus in the Great Smoky Mountains in North Carolina and Tennessee, has long baffled humans who observed the peculiar mating ritual, in which blinking males strive to attract the attention of ground-level females. 

Early-20th-century scientists dismissed the phenomenon as accidental or blamed it on puffs of wind or the twitching eyelids of the people who made these reports, according to one 1935 review in Science.

In the past 50 years, scientists collected anecdotal observations of these unified flashes but not enough empirical data to truly study firefly synchronization’s mechanisms.

Now, Sarfati and Orit Peleg, a physicist and assistant professor also at the University of Colorado, have filmed the mating hordes of P. carolinus and mapped their flashing patterns in three-dimensional space. 

Their research, published Wednesday in the journal Science Advances, adds to evidence that the insects sync their flashes, and suggests what may drive that coordination. TO READ THE ENTIRE ARTICLE, CLICK HERE...