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Saturday, April 17, 2021

Fireflies have a potential -- protective 'musical armor' against bats

How do fireflies defend themselves against predators?

TEL-AVIV UNIVERSITY

IMAGE: NEW STUDY REVEALS: FIREFLIES PRODUCE STRONG ULTRASONIC SOUNDS THAT MIGHT DETER BATS, POTENTIALLY SERVING AS A KIND OF 'MUSICAL ARMOR' AGAINST THESE PREDATORS. view more
CREDIT: BRANDON ALMS

A new study at Tel Aviv University reveals a possible defense mechanism developed by fireflies for protection against bats that might prey on them. According to the study, fireflies produce strong ultrasonic sounds - soundwaves that the human ear, and more importantly the fireflies themselves, cannot detect. The researchers hypothesize that these sounds are meant for the ears of bats, keeping them away from the poisonous fireflies, and thereby serving as a kind of 'musical armor'. The study was led by Prof. Yossi Yovel, Head of the Sagol School of Neuroscience, and a member of the School of Mechanical Engineering and the School of Zoology at the George S. Wise Faculty of Life Sciences. It was conducted in collaboration with the Vietnam Academy of Science and Technology (VAST). The paper was published in iScience.

Fireflies are known for their unique glow, used as a mating signal. Since their bodies contain poison, the light flashes probably also serve as an aposematic signal (a warning to potential predators). This signal is also the firefly's weakness, simply because it makes it an easy target for predators. Bats are among the fireflies' most prevalent potential predators, and some bats have poor vision, rendering the flashing signal ineffective. This led the researchers to check whether fireflies had some additional layer of protection against bats.

Prof. Yossi Yovel explains that the idea for this study came up accidentally, during a study that tracked bats' echolocation. "We were wandering around a tropical forest with microphones capable of recording bats' high frequencies, when suddenly, we detected unfamiliar sounds at similar frequencies, coming from fireflies," he recalls. "In-depth research using high-speed video revealed that the fireflies produce the sound by moving their wings, and that the fireflies themselves can't hear this frequency. Consequently we hypothesized that the sound is not intended for any internal communication within the species," adds Ksenia Krivoruchku, the PhD student who led the study.

Following the accidental discovery, the team at Prof. Yovel's laboratory examined three different species of fireflies that are common in Vietnam (Curtos Luciola, Sclerotia) plus one Israeli species (Lampyroidea), and found that they all produce these unique ultrasonic sounds, but cannot hear them.

Can it be concluded that fireflies have developed a special defense mechanism specifically for bats? Prof. Yovel emphasizes that this claim was not proved in the study, but several features do point to this conclusion. First of all, the fact that the fireflies themselves can't hear the sound, while bats can both hear it and use it to find the fireflies - so it's more likely that it serves as a warning signal. Krivoruochku adds that the discovery of ultrasonic sounds in fireflies is in itself an important contribution to the study of predator-prey relations: "The idea of warning signals that the sender itself cannot detect is known from the world of plants but is quite rare among animals. Our discovery of the 'musical battle' between fireflies and bats may pave the way for further research, and possibly the discovery of a new defense mechanism developed by animals against potential predators."

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Tuesday, February 04, 2020

UPDATED

Biodiversity crisis: Habitat loss, pesticides and light pollution pushing fireflies to extinction, scientists warn
‘Warning bell’ for species as vulnerable ecosystems record impact of heavy industry

Harry Cockburn Tuesday, 4 February, 2020

Gleaming clouds of fireflies glow in a forest at dusk ( Getty )

Fireflies, of which there are more than 2,000 species strobing softly throughout dark corners of the world, are facing grave threats to their continued existence due to the impact of humans, a study suggests.

Habitat loss, pesticide use and artificial light are three of the most serious threats to fireflies, with certain species more at risk than others.

The widespread insects are soft-bodied beetles remarkable for their enchanting use of bioluminescence during twilight to attract mates or prey.

The health of firefly populations helps illustrate the impact humans have on sensitive ecosystems.

To better understand what threats are faced by fireflies, a team led by Professor Sara Lewis at Tufts University, Massachusetts, alongside the International Union for the Conservation of Nature, surveyed firefly experts around the world to assess the most prominent threats to survival for their local species.

Species to be protected by "blue belt" conservation zones

The research, published in the journal Bioscience, “sounds a warning bell” about the insects’ future, highlighting specific threats and the vulnerability of different species across geographical regions.

According to survey respondents, habitat loss is the most critical threat to firefly survival in the majority of geographic regions, followed by light pollution and pesticide use.

“Lots of wildlife species are declining because their habitat is shrinking,” said Professor Lewis.

“So it wasn’t a huge surprise that habitat loss was considered the biggest threat. Some fireflies get hit especially hard when their habitat disappears because they need special conditions to complete their life cycle. For instance, one Malaysian firefly (Pteroptyx tener), famous for its synchronised flash displays, is a mangrove specialist.”

Drastic declines have recently been recorded in this species after the destruction of their mangrove habitat to make way for palm oil plantations and aquaculture farms.

Across the world, light pollution was regarded as the second most serious threat to fireflies.

Artificial light at night has grown exponentially during the last century.

“In addition to disrupting natural biorhythms – including our own – light pollution really messes up firefly mating rituals,” said Avalon Owens, a co-author of the research paper.

Many fireflies rely on bioluminescence to find and attract their mates, and previous work has shown too much artificial light can interfere with these courtship exchanges. Switching to energy efficient, overly bright LEDs is not helping.

“Brighter isn’t necessarily better,” Ms Owens said.

The firefly experts also said the widespread use of pesticides in agriculture was another key threat to firefly survival.

Most insecticide exposure occurs during larval stages, because juvenile fireflies spend up to two years living below ground or under water.

Insecticides such as organophosphates and neonicotinoids are designed to kill pests, yet they also have off-target effects on beneficial insects. While more research is needed, the evidence suggests many commonly used insecticides are harmful to fireflies.

The paper acknowledges previous studies which have quantified firefly population declines, such as those seen in the tourist-attracting synchronous fireflies of Malaysia, and the glowworm Lampyris noctiluca in England.

Numerous anecdotal reports suggest that many other firefly species across a wide range of habitats have also suffered recent declines.

“We really need better long-term data about firefly population trends. This is a place where citizen science efforts like Massachusetts Audubon’s Firefly Watch project can really help,” said Professor Lewis.

The researchers also highlighted risk factors that allow them to predict which species will be most vulnerable when faced with threats like habitat loss or light pollution. For instance, females of the Appalachian blue ghost firefly (Phausis reticulata) are flightless.

“So when their habitat disappears, they can’t just pick up and move somewhere else,” said co-author J Michael Reed, professor of biology at Tufts.

Despite the verdict the researchers remain optimistic about fireflies’ future.

“Here in the US, we’re fortunate to have some robust species like the Big Dipper fireflies (Photinus pyralis),” said Professor Lewis.

“Those guys can survive pretty much anywhere, and they’re beautiful, too.”

By illuminating these threats and evaluating the conservation status of firefly species around the world, researchers aim to preserve the magical lights of fireflies for future generations to enjoy.

“Our goal is to make this knowledge available for land managers, policy makers, and firefly fans everywhere,” said co-author Sonny Wong of the Malaysian Nature Society.

“We want to keep fireflies lighting up our nights for a long, long time.”

Blinded by the light, firefly species face extinction

TUFTS UNIVERSITY/AFP / Jason STEELFireflies are beetles that glow to attract a mate

Fireflies are in deep trouble, with many species facing extinction due to habitat loss and exposure to pesticides, according to the first major review of their global status, published Monday.

Adding irony to injury, one of Nature's most entrancing spectacles is also being snuffed out by artificial light pollution, researchers reported in the journal BioScience.

More than 2,000 species of fireflies -- which are, in fact, beetles -- illuminate wetlands, marshes, grasslands, forests and urban parks worldwide.

A few, such as the Big Dipper in the United States, seem to be flourishing.

"Those guys can survive pretty much anywhere," said Sara Lewis, a biologist at Tufts University in Massachusetts and lead author of the study, based on a survey of dozens of firefly experts.

But other varieties -- from the glowworms of southern England to Malaysia's synchronous fireflies and the Appalachian blue ghost, both of which draw tourists -- are being extinguished by humanity's ever-expanding ecological footprint.

AFP/File / STRArtificial light, habitat loss and pesticides pose a grave threat to firefly species

"Some species get hit especially hard by habitat loss because they need specific conditions to complete their life cycle," said Lewis.

The Malaysian firefly Pteroptyx tener, for example, lives during its larval phase in riverside mangroves, many of which have been ripped up to make way for palm oil plantations and fish farms.

The glowworm (L. noctiluca) has another problem -- females are flightless, which means that can't simply buzz off to a new location when their habitat is swallowed by a suburb, commercial crop or country road.

Other species of fireflies, which eat only during their larval phase, are "dietary specialists," meaning they subsist on one or two kinds of snail, earthworm or other soft-bodied prey.

When fruit orchards in Mediterranean Spain are abandoned or give way to urbanisation, so too do the snails preferred by aptly named Lampyris iberica, leaving the firefly larva nothing to eat.

- 'Flashing through the gloom' -

Adult Pteroptyx in Malaysia, meanwhile, gather for nightly courtship displays in specific trees located along mangrove rivers. Many of those trees have been cut down.

Of 10 possible drivers of extinction, experts fingered habitat loss as the top threat everywhere -- except east Asia and South America.

In those two regions, artificial light was seen as the biggest menace to the world's luminescent beetles.

"In addition to disrupting natural biorhythms, light pollution really messes up firefly mating rituals," said co-author Avalon Owens, a doctoral student at Tufts.

Many species of firefly depend on their ability to light up to find and attract mates.

TUFTS UNIVERSITY/AFP/File / RADIM SCHREIBEROne of Nature's most entrancing spectacles -- fireflies -- is also being snuffed out by artificial light pollution

To make matters worse, that window of opportunity is very narrow: while the firefly larval phase lasts months to years, adults typically live only a few days.

The twinkling beetles are so focused on reproducing that they don't even eat.

The survey found that fireflies are also being decimated by commonly used insecticides, the third major threat.

"Organophosphates and neonicotinoids are designed to kill pests, yet they also have off-target effects on beneficial insects," the researchers wrote.

Fireflies light up by triggering a chemical reaction –- involving oxygen, calcium and an enzyme called luciferase -- inside special organs in their abdomen, a process called bioluminescence.

Their otherworldly glow has been an enduring source of fascination.

But firefly tourism -- long popular in Japan, Malaysia and Taiwan -- has also taken a toll, with fragile ecosystems damaged by too much foot traffic.

The plight of fireflies at the beginning of the 21st century add a new layer of meaning to lines written more than a century ago by Canadian poet Bliss Carman.

"And the fireflies across the dusk, Are flashing signals through the gloom," he wrote.

While climate change is not seen as a current threat, future sea level rise and drought also could accelerate the drive towards extinction.

The dozen authors contributing to the study are all affiliated with the Firefly Specialist Group -- set up in 2018 -- of the International Union for the Conservation of Nature (IUCN), which compiles the Red List of threatened species.

Thursday, August 28, 2025

ARACHNOLOGY

Spider uses trapped fireflies as glowing bait to attract more prey

British Ecological Society

image:
Sheet web spider with fireflies caught in web
view more
Credit: Tunghai University Spider

Ecologists have observed a species of nocturnal spider attracting prey to its web using the bioluminescent beacons of already trapped fireflies. This rare example of a predator exploiting its prey’s mating signal for its own gain is documented in the British Ecological Society’s Journal of Animal Ecology.

Researchers at Tunghai University, Taiwan have observed sheet web spiders Psechrus clavis capturing fireflies in their webs and leaving them there while they emitted bioluminescent light for up to an hour. The researchers even observed the spiders going to check on the captured fireflies from time to time.

Intrigued by this unusual behaviour the researchers set up an experiment to test whether this was a strategy used by the spiders to increase their hunting success. In the experiment, they placed LEDs that resembled fireflies, in real sheet spider webs and left other webs clear as controls.

They found three times the amount of prey was attracted to webs with the LEDs compared to the control webs. This increased to ten times more prey when they only looked at fireflies being captured.

The findings confirm that captured fireflies left as bait increase the hunting success rate of the spiders. The researchers also noticed that the majority of captured fireflies were male, who were likely mistaking the glow for potential mates.

Dr I-Min Tso, the lead author of the study said: “Our findings highlight a previously undocumented interaction where firefly signals, intended for sexual communication, are also beneficial to spiders.

“This study sheds new light on the ways that nocturnal sit-and-wait predators can rise to the challenges of attracting prey and provides a unique perspective on the complexity of predator-prey interactions.”

The researchers suggest that this behaviour could have developed in sheet web spiders to avoid costly investment in their own bioluminescence like other sit-and-wait predators, such as anglerfish. Instead, the spiders are able to outsource prey attraction to their prey’s own signals.

The sheet web spider Psechrus clavis is a nocturnal sit and wait predator found in subtropical forests of East Asia. It’s main source of prey, the winter firefly Diaphanes lampyroides, uses continuous, non-flashing bioluminescence to attract mates.

Video footage captured by the researchers in their experiment shows sheet web spiders employing different strategies when interacting with different prey species. Spiders would immediately consume any moths captured in their webs but would not immediately consume fireflies they captured.

“Handling prey in different ways suggests that the spider can use some kind of cue to distinguish between the prey species they capture and determine an appropriate response.” explained Dr I-Min Tso. “We speculate that it is probably the bioluminescent signals of the fireflies that are used to identify fireflies enabling spiders to adjust their prey handling behavior accordingly.”

The researchers conducted their field experiment in the conifer plantation forest at National Taiwan University’s Xitou Nature Educational Area.

Because they used LEDs to mimic the light signal emitted by fireflies, the researchers warn that although the wavelength and intensity of the LED set up was a close match to fireflies, it would be best if real fireflies were used in the field experiment. But they admit that this would be extremely difficult in practice.

-ENDS-

Journal

Journal of Animal Ecology

DOI

10.1111/1365-2656.70102

Method of Research

Observational study

Subject of Research

Animals

Friday, February 07, 2020

Fireflies face extinction risk - and tourists are partly to blame
By Georgina Rannard BBC News

GETTY IMAGES
Firefly tourism is growing in countries including Mexico,
Japan, Malaysia and India

Firefly tourism is on the rise globally but scientists are warning it may contribute to risk of the insect's extinction.

"I spotted a hundred flickering lights, illuminating a palm like a Christmas tree."

"Our guide waved his flashlight at the fireflies. They slowly engulfed us - we were surrounded by a shiny galaxy of glowing beetle stomachs."

"I reached out a hand and captured one in my fist."

Reading this travel blogger's enchanting experience in 2019 makes it clear why firefly tours are popular, but done badly, it risks killing the insects.

Habitat loss and light pollution from urbanisation and industrialisation are the leading threats to firefly populations, according to research published this week.

But firefly tourism, which attracts thousands of visitors in countries including Mexico, the US, the Philippines and Thailand, is a growing concern for conservationists.

"Getting out into the night and enjoying fireflies in their natural habitat is an awe-inspiring experience," Prof Sara Lewis at Tufts University, who led the research, told the BBC.

But tourists often inadvertently kill fireflies by stepping on them, or disturb their habitat by shining lights and causing soil erosion.

Firefly festivals are organised in countries including Japan, Belgium, and India, and social media is magnifying this tourism, she adds.
How tourism can kill fireflies

The tiny town of Nanacamilpa in Mexico became a celebrated firefly spot in the past decade.

Some visitors post their sparkling photos on Instagram, flouting the ban on photography that many site managers impose, says local photographer Pedro Berruecos.

The Mexican fireflies are especially vulnerable to tourists, Prof Lewis explains.

Estimated annual visitors to firefly sites
Malaysia: 80,000
Great Smoky Mountains, Tennessee: 30,000 in two-three week summer season
Taiwan: 90,000
Mexico: 200,000 in 2019, up from 180,000 in 2018

The female insects are wingless and cannot fly, meaning they live on the ground, where visitors walking around will trample on them.

"No blame on the tourists, but if they walk on the forest floor, they will be standing on the female fireflies who will be carrying eggs. They are killing the next generation," Prof Lewis says.

In Thailand, Malaysia and the Philippines, the industry has existed for a few decades, but is usually poorly-managed, she explains.

PEDRO BERRUECOS
Firefly season is just three months in Mexico meaning the
concentrated visits put extra pressure on the eco-system

Congregating Mangrove fireflies live exclusively in mangrove trees along rivers.

Males gather in huge numbers to attract females, producing the appealing glowing swarms that tourists desire.

Motorised boats are driven up the rivers, creating water swells that erode the banks, killing the trees where the fireflies live.

You might also like:
The 'unnoticed insect apocalypse': How people in towns and cities can help

"Operators also crash boats into the banks to disturb trees and make fireflies fly out, creating a swarm for tourists to see," Prof Lewis explains.

"There is evidence that even just camera flashes disturb fireflies and interfere with their reproductive success, in addition to the flashlights used by tourists".
Is firefly eco-tourism even possible?

Prof Lewis is keen to emphasise that firefly tourism is often crucial to local economies and should not be banned.

Instead tour operators and tourists can develop eco-friendly practices.

KATIE DIEDERICHSImage
Travel bloggers rave about their firefly experiences -
Katie Diederichs chose an eco-friendly tour operator

Travel blogger Katie Diederichs and her husband, both from the US, chose an eco-friendly tour operator in Bohol, Philippines for their firefly experience in 2015.

Travelling in a small group at night in kayaks with just one light, the experience was designed to be as unobtrusive as possible, Katie explains.

"The amount of light from the fireflies made the mangroves look like Christmas trees - it was really magical.

Chief Raoni Metuktire's fight to save the Amazon rainforest

"The male fireflies were flying around, giving the illusion of twinkling, while the females blink."

The company is run by locals who love the fireflies and want to protect their environment, she explains.

But Katie says they witnessed other operators with "large motorboat of tourists" passing by them "sending waves in our direction."

CARLA RHODES PHOTOGRAPHY

Wildlife conservation photographer Carla Rhodes snaps
the Big Dipper Firefly in the Catskill Mountains in New York, US

In Taiwan, the tourist board has invested in sustainable firefly tours and created "thoughtful and effective" firefly eco-tourism, Prof Lewis explains.

Sites have regulated guided tours with raised walkways that allow small groups of people to walk through the habitat without trampling on fireflies.

Instead of flashlights or headlamps that would disturb the insects, white paint illuminates the routes.

A group of scientists will meet in 2020 to set down guidelines for how to run a sustainable firefly tourism company, Prof Lewis says.

A photographer's tips for snapping responsibly

"It is very important to not disturb the fireflies' habitat while photographing," advises wildlife conservation photographer Carla Rhodes.

She regularly photographs the Big Dipper firefly, as well as other wildlife, where she lives in the Catskill mountains in New York.

Watch where you walk, she says, and be careful with your light sources.

"And for goodness sake, please don't ever capture them!"

SEE https://plawiuk.blogspot.com/search?q=FIREFLIES

Monday, April 29, 2024

Fading lights: Comprehensive study unveils multiple threats to North America’s firefly populations

As cities grow, they encroach on firefly natural habitats reducing their populations. A multi-university study is hoping to begin reversing the decline of this critical insect.

UNIVERSITY OF KENTUCKY

A landmark study conducted by the University of Kentucky Martin-Gatton College of Agriculture, Food and Environment; Bucknell University; Penn State University; and the USDA has shed light onto the precarious situation facing firefly populations across North America. The study’s results identified multiple factors impacting their numbers, offering a deep dive into how shifting environmental and human factors influence these iconic insects.

The study, published in Science of the Total Environment, “Illuminating Patterns of Firefly Abundance Using Citizen Science Data and Machine Learning Models,” identified the factors likely responsible for troubling declines in firefly populations across North America. To study these population changes, the research used a mix of field surveys from citizen scientists and advanced machine learning techniques to analyze over 24,000 surveys from the Firefly Watch citizen science initiative.

Key Findings

This research marks the first comprehensive attempt to apply a data-driven approach to understanding firefly population dynamics on a continental scale. Key findings from this new study indicate that fireflies, part of the beetle order, are sensitive to various environmental factors, from short-term weather conditions to longer climatic trends, including the number of growing-degree days related to temperature accumulations.

“Subtle changes in climate patterns, especially related to temperature, are significantly impacting firefly breeding cycles and habitat quality,” said Darin McNeil, study principal investigator and assistant professor of wildlife ecology and management.

Christina Grozinger, publius vergilius maro professor of entomology at Penn State University, said while scientists previously knew that urbanization, agricultural intensification and climate change can affect biodiversity, less was known about how these complex factors interact and what people can do in their own backyards, towns and cities to support biodiversity.

“In this study, we integrated large scale data sets on species abundance, land use, soil type, weather and climate using machine learning models to precisely model and predict firefly abundance patterns at the local scale across the eastern U.S.,” Grozinger said. “We were very fortunate to have a multi-year citizen science data set that spanned more than 24,000 observations.”

The study underscores fireflies' sensitivity to climatic variables such as temperature and precipitation. Fireflies thrive in temperate conditions, with wet and warm summers creating the ideal breeding environment and cold winters supporting the survival of immature stages like eggs, larvae and pupae.

However, as global temperatures rise, these conditions become less predictable and, often, less hospitable. Changes in precipitation patterns, another critical factor for firefly survival, have led to either overly dry conditions that reduce larval survival or excessively wet conditions that can flood breeding grounds and disrupt life cycles.

“Artificial lights at night could disrupt firefly populations, possibly affecting both adult and larval stages,” McNeil said. “Firefly larvae, which live in the soil, are particularly vulnerable to changes in light exposure and artificial light could alter their developmental cycles and survival rates. Firefly larvae, which are predatory, also require moist soil conditions because the humidity supports soft-bodied invertebrates like snails and slugs that firefly larvae use as prey.”

Urban growth, such as establishing impervious surfaces such as sidewalks, buildings and roads, poses a significant threat to firefly populations by invading natural habitats and decreasing available breeding areas. Light pollution from streetlights and commercial signs is particularly disruptive, as it interferes with the fireflies' bioluminescent communication essential for mating. The study indicates that fireflies are markedly less common in areas with significant nighttime light pollution.

Agriculture impact on fireflies

Certain agricultural practices also seem to contribute to the decline of fireflies. The extensive use of pesticides and herbicides has been linked to decreased firefly numbers, likely due to reduced prey availability and direct toxicity. This new study did not find a pesticide effect; in fact, certain agricultural areas supported some of the highest firefly densities, perhaps because some practices (e.g., livestock grazing) support meadow-like conditions that benefit fireflies. The study warns against increasing agricultural intensification, especially practices that reduce the organic debris and moist environments firefly larvae require to thrive.

The paper reveals that the decline in firefly populations is not uniform across all climates or regions. Some species adapted to dryer environments or those with specific breeding patterns may be less affected by certain changes, whereas others are more vulnerable. This highlights the complexity of natural ecosystems and the need for tailored conservation strategies.

The research team also made significant strides in identifying potential conservation measures to mitigate these impacts. These include reducing light pollution, preserving natural habitats and implementing wildlife-friendly agricultural practices that support fireflies.

Fireflies’ importance in the environment

The decline of fireflies is more than the loss of a beloved natural spectacle; it signals broader ecological disruptions that could have cascading effects on other species and ecosystems. Fireflies play a role in the food web, serving as prey for some species and as predators for many invertebrates. Their disappearance could have unforeseen repercussions on local biodiversity.

“As the study concludes, further research is encouraged, particularly in exploring the long-term trends of firefly populations and the efficacy of various conservation strategies” McNeil said. “Moving forward, focused studies that survey particular firefly species, rather than the firefly community as a whole, will be important. This approach will be crucial in ensuring that future generations can also enjoy the natural wonder of fireflies lighting up the night sky.”

“Each individual species has its own habitat requirement and things it needs to succeed,” adds Bucknell University assistant professor of biology Sarah Lower, a noted firefly researcher. “With the citizen science data in this study, we’re looking at fireflies in the aggregate, but we would like people in citizen science getting more training in species identification. If we can get species-level information, we can provide more specifics on species living in a particular area and how best to protect them.”

To create similar data sets for other firefly species, the research team is also leveraging technology and AI to develop automated monitoring systems through an NSF funded INSECT NET graduate training program.

Individuals interested in learning more about the land use, weather and climate conditions in their locations can use Penn State's Beescape tool, which provides location-specific habitat quality scores for pollinators.

This work was funded by the Penn State Insect Biodiversity Center, Penn State’s Huck Institutes of the Life Sciences and Penn State’s College of Agricultural Sciences via the USDA’s National Institute of Food and Agriculture and Hatch Appropriations.

JOURNAL

Science of The Total Environment

DOI

10.1016/j.scitotenv.2024.172329

METHOD OF RESEARCH

Survey

SUBJECT OF RESEARCH

Animals

ARTICLE TITLE

Illuminating patterns of firefly abundance using citizen science data and machine learning models

COI STATEMENT

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Friday, November 04, 2022

Pitt mathematicians explain how some fireflies flash in sync

Peer-Reviewed Publication

UNIVERSITY OF PITTSBURGH

Stake out in Pennsylvania’s Cook State Forest at the right time of year and you can see one of nature’s great light shows: swarms of fireflies that synchronize their flashes like strings of Christmas lights in the dark.

A new study by Pitt mathematicians shows that math borrowed from neuroscience can describe how swarms of these unique insects coordinate their light show, capturing key details about how they behave in the wild.

“This firefly has a quick sequence of flashes, and then a big pause before the next burst,” said Jonathan Rubin, professor and chair of the Department of Mathematics in the Kenneth P. Dietrich School of Arts and Sciences. “We knew a good framework for modeling this that could capture a lot of the features, and we were curious how far we could push it.”

Male fireflies produce a glow from their abdomens to call out to potential mates, sending out blinking patterns in the dark to woo females of their own species. Synchronous fireflies of the species Photinus carolinus take it a step further, coordinating their blinking throughout entire swarms. It’s a rare trait — there are only a handful of such species in North America — and the striking lights they produce draw crowds to locations where the insects are known to gather.

They’ve also attracted the interest of mathematicians seeking to understand how they synchronize their blinks. It’s just one example of how synchronization can evolve from randomness, a process that has intrigued mathematicians for centuries. One famous example from the 1600s showed that pendulum clocks hung next to one another synchronize through vibrations that travel through the wall, and the same branch of math can be used to describe everything from the action of intestines to audience members clapping.

“Synchrony is important for a lot of things, good and bad,” said co-author Bard Ermentrout, distinguished professor of mathematics in the Dietrich School. “Physicists, mathematicians, we’re all interested in synchronization.”

To crack the fireflies’ light show, the Pitt team used a more complex model called an “elliptic burster” that’s used to describe the behavior of brain cells. The duo, along with then-undergrad Madeline McCrea (A&S ’22) published details of their model Oct. 26 in the Journal of the Royal Society Interface.

The first step was to simulate the blinks of a single firefly, then expand to a pair to see how they matched their flashing rates to one another. Next, the team moved to a bigger swarm of simulated insects to see how number, distance and flying speed affect the resulting blinks.

Varying the distances each firefly could “see” each other and respond to one another changed the insects’ light show, they found: By tweaking the parameters, they could produce patterns of blinks that looked like either ripples or spirals.

The results line up with several recently published observations about real-life synchronous fireflies — for instance, that individual fireflies are inconsistent while groups flash more regularly, and that when new fireflies join the swarm, they’re already perfectly in time.

“It captured a lot of the finer details that they saw in the biology, which was cool,” said Ermentrout. “We didn't expect that.”

The math also makes some predictions that could inform firefly research — for instance, light pollution and the time of day both may alter the patterns produced by fireflies by changing how well they can see one another’s blinks.

McCrea worked on the research as an undergraduate supported by the department’s Painter Fellowship, which gave her funding to work on the project through the summer. “She was awesome working on this project, and really persistent,” said Rubin.

The team is the first to use this particular brain-cell framework to model fireflies, which several different research teams are trying to understand using different types of math. “It’s more of a wild west research topic,” said Ermentrout. “It’s early days, and who knows where things are going to go from here?”

Ermentrout and Rubin also hopeful that the math will capture the imagination of those inspired by the glow of fireflies. In the midst of this project, Rubin himself decided to head up to Cook State Forest to see if he could spot his research subjects firsthand.

“I convinced my wife to go on a trip for a couple of days right in the peak of the season,” he said. “It’s not clear we ever saw synchronized activity, but there were all sorts of fireflies around us. It was amazing.”