How Do Fireflies Flash in Sync? Studies Suggest a New Answer.

They symbolize leaving souls in Japanese folk traditions. The eyes of ghosts are seen by some Indigenous cultures. Children, crop, doom, elves, fear, habitat change, idyll, love, luck, mortality, prostitution, and many other metaphors have been associated with bioluminescent beetles.

Physicists believe that a few species of fireflies have the ability to flash in sync with one another. In Malaysia and Thailand, firefly- studded mangrove trees can blink on beat as if strung up with Christmas lights. The light shows of the fireflies have helped spark some of the most fundamental attempts to explain coordination, even though they have helped lure mates and crowds of humans.

As an undergrad, Orit Peleg first encountered the mystery of synchronous fireflies. A textbook by the mathematician Steven Strogatz was used by her class to show how simple systems can achieve synchrony. In Israel, where she grew up, a firefly is rare.

She said that it stuck in her head for a long time. By the time she started her lab at the University of Colorado and the Santa Fe Institute, she had learned that quantitative data describing what the insects were actually doing wasn't very useful.

She wanted to fix that. In the last two years, a series of papers from Peleg's group have opened a fire hose of real-world data about synchrony in multiple firefly species at multiple study sites. Bard Ermentrout, a mathematical Biologist at the University of Pittsburgh, described the team's results to a group of people. Andrew was a Biologist at the University of Connecticut.

The papers show that firefly swarms are different from the mathematical idealizations that have been used for decades. Every model for firefly synchrony assumes that each firefly has its own internal clock. In at least one species, individual fireflies have no rhythm, and it was shown that a collective beat emerges only from the spooky synergy of many lightning bugs. A rare type of synchrony that mathematicians call a chimera state, which has almost never been observed in the real world outside of contrived experiments, was documented in a preprint uploaded in May and updated last week.

The new methods will change the way the science of fireflies is done. Strogatz described in his textbook the types of theories that mathematicians have been cranking out for a long time. Strogatz is a professor at Cornell University. We can begin to close the loop now.

The Elusive Proof of Synchrony

The reports of fireflies in Southeast Asia went back hundreds of years. There are thousands of kelip-kelip in Malaysia and they can be found on riverside trees. The British diplomat wrote about the fires in Thailand in 1856. Every leaf and branch is adorned with fire.

Some people didn't accept the reports. In 1917, a letter to the journal Science argued that the effect was caused by the viewer blinking, rather than the insect. By the 1960s, visiting firefly researchers were able to confirm what local boatmen had known.

In the 1990s, a Tennessee naturalist named Lynn Faust read a scientist's statement that there were no synchronous fireflies in the US. Faust knew what she was seeing when she was in the woods.

The species of Photinus carolinus is found in the Great Smoky Mountains. There are clouds of male fireflies in the sky. The fireflies emit a burst of quick flashes within a few seconds, then go quiet for several times before losing another burst. Imagine a crowd of people waiting for celebrities to show up, snapping photos at each appearance, and then twiddling their thumbs in the downtime.

The evolutionary mystery of how to blend in with a potential mate has always been posed.

The isolated firefly tried to flash on beat with a neighboring firefly in a jar. High-sensitivity video cameras were set up at the edges of fields and forest clearings. The footage was counted by the number of fireflies illuminated at a time. Statistical analysis of this painstakingly gathered data proved that all the fireflies within the cameras view at a scene really did emit flash bursts.

Better technology was available when Peleg and her colleague, the physicist Raphal sarfati, set out to collect firefly data. A system of two cameras was designed. The dynamics of firefly swarms can be captured from within, not just from the side. Instead of counting flashes by hand, Sarfati came up with a way to triangulate firefly flashes caught by both cameras and then record where they happened.

The system was brought into the field in Tennessee in the summer of 2019. He had never seen a spectacle with his own eyes. The Tennessee bursts were messier, with bursts of up to eight quick flashes over about four seconds repeated roughly every 12 seconds. He felt that a system with wild fluctuations could be more informative than one that behaved perfectly. He said it was complex but also beautiful.

Random but Sympathetic Flashers

She learned to understand them through a model proposed by the Japanese physicist. The granddaddy of mathematical schemes that explain how synchrony can arise is the ur-model of synchrony.

Models of synchronous systems have to describe two processes. In the case of a lone firefly in a jar, the inner dynamics of an isolated individual are governed by a behavioral rule. The flash of a firefly influences its neighbors. A lot of different agents can pull itself into a neat chorus.

Each firefly is described in a way that makes it sound like it has a preferred rhythm. Imagine a bug flashing every time its pendulum sweeps through the bottom of it's arcs, as if it were a hidden pendulum. A firefly's pace-setting pendulum might be pulled forward or back by a neighboring flash. A collective governed by these rules will often converge on a coordinated flash pattern even if the fireflies start off out of sync.

Over the years there have been several variations on this general scheme. Strogatz and Rennie Mirollo of Boston College showed in 1990 that a very simple set of firefly-like oscillators would almost always work if you connected them. In the next year, Ermentrout explained how groups of Pteroptyx malaccae fireflies in Southeast Asia could sync up. A group led by Gonzalo Ramrez-vila of the Higher University of San Andrés in Bolivia came up with a scheme in which fireflies could switch between acharging and discharging state.

New patterns were revealed when the cameras were used to capture three-dimensional data from the Photinus Carolinus fireflies.

Faust and other firefly biologists had long reported that a burst of flashes would cascade through the forest at half a meter per second. The ripples suggested that the fireflies were not global, but local, and that each firefly cared only about their neighbors. The fireflies paid attention to other fireflies at different distances. In the forests, vegetation often gets in the way, so it's possible that the fireflies can only see flashes that occur within an unimpeded sightline.

The core premise of the models is that each individual is treated as a variable. The firefly emitted flashes of light when it was released in a tent. Sometimes it only took a few seconds, other times it took a long time. Strogatz said that taking you out of the universe of existing models is already done.

The entire tent lit up with flash burst after the team dumped in 15 or more fireflies. The periodicity and the synchrony were created by the fireflies. A new model for how this could happen was suggested in a draft paper uploaded to the preprint server.

Consider the following rules if you were to imagine a firefly that just emitted a burst of light. It will wait for a random interval before flashing again if it's sequestered now. The insect needs a minimum wait time to be able to use its light organs. If another firefly starts to flash, this firefly will flash as well.

Imagine a field of firefly in the dark after a burst. Each person chooses a wait time that is longer than the charging time. Everyone jumps in immediately if someone flashes first. Each time the field goes dark, this process is repeated. As the number of fireflies increases, at least one will randomly choose to flash again as soon as possible, and that will set off the rest. The time between bursts shortens because of this. There is a steady group of light rolling into darkness, and then there is a sudden burst of light.

Another pattern was found in a second preprint. When her team trained their equipment on the firefly Photuris frontalis, they noticed something odd. There is a small firefly in the corner of my eye. She stated that he is still on time.

Firefly have been doing computer science for a long time.

Stubborn outliers refused to play along with the main chorus of the fireflies. They flashed with their own period but were out of sync with the symphony. Sometimes the outliers were synchronized with each other. This is a chimera state, a form of synchrony first noted by Kuramoto in 2001 and explored by Strogatz and the mathematician DanielAbrams in 2004. The activity of brain cells under certain experimental conditions is what a few reports from neuroscientists claim to have seen.

It is not clear why nature would prefer the evolution of a patchwork state of syncretization. Even basic synchrony has posed an evolutionary mystery: How does a single man stand out to a mate? There are studies looking at the behavioral patterns of females and not just males. The group has started to do that with the P. frontalis species.

Lightning-Bug Computer Science

The observed firefly patterns need to be encapsulated in new frameworks. Ermentrout has a paper under review that offers a different mathematical description of Photinus carolinus. When gathered together, the fireflies could act like periodic flashers. The model is similar to the data of the group. The waves emerge even though we didn't program it in.

The camera-and-algorithm system may help to advance firefly research. Fireflies are difficult to study in the wild because they are hard to tell apart. It's difficult to measure the range and abundance of firefly populations because of the fear that many lightning bug species are on the verge of extinction. It's easier to collect, analyze and share firefly- flashing data with the new setup.

The system was used to confirm a report from Arizona that the local species of Photinus knulli can sync up. The firefly researchers in the US received 10 copies of the camera system this year. A group of machine learning researchers are trying to learn how to identify species from the recorded footage.

Modelling of fireflies inspired mathematical theory for a long time.

That hope is shared by the man. He said that fire flies have been doing computer science. A better grasp of self-organizing behaviors in other living things could be achieved by learning how they sync.

Steven Strogatz is a member of the advisory board of Quanta.

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