A similar scenario played out in the 1990s, when Tennessee naturalists named Lynn Faust read a man named Jon Copeland There are no synchronized fireflies in North America. Faust knew then that what she had been seeing in the nearby woods for decades was a remarkable thing.
Faust invited Copeland and his collaborator Moiseff to see a species in the Great Smoky Mountains called heatherSwarms of male fireflies fill forests and clearings, floating at about human height. Instead of blinking in tightly coordinated fashion, these fireflies emit a burst of rapid flashes over the course of a few seconds, then go quiet several times before losing another flash. (Imagine a group of paparazzi waiting for a celebrity to show up at regular intervals, taking a barrage of photos each time they show up, and then twiddling their thumbs in their free time.)
Copeland and Moiseff’s experiments showed that isolated P. carolinus Fireflies do try to blink with neighboring fireflies or with blinking LED lights in nearby jars. The team also set up highly sensitive cameras on the edges of fields and forest clearings to record the flashes. Copeland went through the footage frame by frame, counting how many fireflies were illuminated at each moment. Statistical analysis of this painstakingly collected data proved that all fireflies within the camera’s field of view in a scene indeed flashed at regular, correlated intervals.
Twenty years later, when Peleg and her postdoc, the physicist Rafael Sarfati, set out to collect firefly data, better techniques become available. They designed a system consisting of two GoPro cameras placed a few feet apart. Because the cameras capture 360-degree video, they can capture the movement of the firefly swarm from the inside, not just from the side. Instead of manually counting flashes, Sarfati devised processing algorithms that triangulated the firefly flashes captured by the two cameras and then recorded not only when each flash occurred, but also where in three-dimensional space it occurred.
Sarfati first introduced the system to its Tennessee site in June 2019 for P. carolinus The Firefly of Faust fame. This was the first time he had seen such a spectacle with his own eyes. He had imagined a tight scene similar to the synchronization of fireflies from Asia, but the Tennessee bursts were more chaotic, repeating roughly every 12 seconds, with up to eight rapid flashes in about four seconds. Yet the chaos is exciting: As a physicist, he thinks a system with wild fluctuations can prove to be far more informative than a perfectly behaving system. “It’s complex, confusing in a sense, but also beautiful,” he said.
random but sympathetic flash
When Peleg studied synchronous fireflies as an undergraduate, he first learned to understand them through a model formalized by Japanese physicists Yoshiki Kuramoto, based on earlier work by theoretical biologist Art Winfree. This is the most primitive model of synchronization, the granddaddy of the mathematical schemes that explain how synchronization arises, often unavoidably, from populations of pacemaker cells in the human heart to alternating current.
At its most basic, a synchronization system model needs to describe two processes. One is the internal dynamics of an isolated individual—in this case, a solitary firefly in a jar, governed by physiological or behavioral rules that determine when it blinks. The second is what mathematicians call coupling, the way one firefly’s flash affects its neighbors. Through the fortuitous combination of these two parts, the cacophony of different agents can quickly transform itself into a neat chorus.
In Kuramoto-style descriptions, each firefly is viewed as an oscillator with an inherently preferred rhythm. Think of fireflies as having a hidden pendulum swinging steadily inside them; imagine a bug flashing every time its pendulum sweeps the bottom of the arc. Suppose also that seeing a neighboring flash of light pulls the firefly’s speeding pendulum slightly forward or backward. Even if fireflies are initially out of sync with each other, or their preferred internal rhythms vary, collectives governed by these rules often converge on coordinated flash patterns.
Several variants of this general scheme have emerged over the years, each tweaking the rules of internal dynamics and coupling. In 1990, Strogatz and his colleagues Renee Mirolo Boston College demonstrated that if you interconnect a set of very simple firefly-like oscillators, they are almost always in sync, no matter how many individuals you include.The following year, Ermentrout described a group of Malacca Pterosaur Fireflies in Southeast Asia can synchronize by speeding up or slowing down their internal frequencies.Just in 2018, a Gonzalo Marcelo Ramirez-Avila Researchers at the Higher University of San Andrés in Bolivia devised a more complex scheme, in which fireflies switch back and forth between a “charged” state and a “discharged” state, during which time they blink.