Fireflies are flourishing in places you wouldn't expect

National Geographic

11-07-2025

Pesticides, habitat loss, and light pollution are threatening firefly populations worldwide, but even in urban areas, some lightning bugs continue to shine. Photographs by Sriram Murali
For many people across the United States, summer doesn't truly begin until the soft glow of electric yellow and green fireflies can be seen drifting through the night.
But you don't have to travel to the deep woods or open prairie to experience these otherworldly insects. In fact, several firefly species can be found quietly blinking in the heart of some of the United States' largest cities.
'It's the last place you would expect to see fireflies,' says Sriram Murali, an International Union for Conservation of Nature Species Survival Commission firefly specialist and National Geographic Explorer.
This summer, Murali traveled to New York City and Washington, D.C. to photograph urban fireflies as a way to show how resilient some species are in the face of one of their greatest threats—light pollution. Dot-dash fireflies (Photuris pensylvanica) are seen on Roosevelt Island near the Kennedy Center in Washington, D.C., in a composite photograph made from 194 two-second exposures. Areas closer to light pollution show reduced firefly activity, with noticeably shorter streaks.
'Where I live in a small town in India, people hardly think about the impacts of lighting, because we can close our curtains and sleep peacefully at night,' he says. 'But there's so much nocturnal wildlife, even in towns and cities, such as owls, frogs, and snakes, that need darkness.'
And yet, even in cities that never sleep, some fireflies, such as the common Eastern firefly (Photinus pyralis) have found a way to make do. Murali even discovered a rare population of the vulnerable dot-dash firefly (Photuris pensylvanica) lighting up the night during a photoshoot on Roosevelt Island in Washington, D.C. Where guests are guardians
'To me, it's more philosophical, and it's about how much change we've done to our environment,' says Murali. 'That an insect which has evolved over hundreds of millions of years has had to adapt to so much.
'They deserve their rightful place as much as we do,' he says.
Also known as big dippers for the J-shaped flash pattern they make, common Eastern fireflies are one of the most frequently spotted fireflies in eastern U.S. cities, says Gabriel Willow, an urban naturalist living in Brooklyn.
From Central Park's rolling greens and pollinator meadows to soccer and baseball fields, Willow says the best way to see these bioluminescent beetles is to go looking in late June.
'It has to be warm enough, and they have to have enough time to metamorphize from the larval stage to the adult stage, which is when you start seeing them flying and flashing and looking for a mate,' says Willow. 'They're pretty easy to find.' Dot-dash fireflies (Photuris pensylvanica) are seen on Roosevelt Island in Washington, D.C., in a composite photograph made from 516 two-second exposures. This species of fireflies glows while flying vertically. Common eastern fireflies (Photinus pyralis) are seen at The Battery in New York City, in a composite photograph made from 2,118 half-second exposures. Fireflies of this species are notable for the "J" shape they make while they glow.
Grassy areas are a particularly good place to look for fireflies. Pesticide use in grassy urban areas is generally less of a problem than in suburbs—although cities often do spray for mosquitoes, which likely affects firefly populations too.
As someone who regularly conducts urban wildlife tours, Willow says he likes to remind people that many major cities sprouted up around areas that were exceptionally biodiverse.
'New York City is located within an estuary, and that means you have lots of sea life, but also migrating birds,' he says. 'Los Angeles was built on a former wetland, and if you look at London or Paris, they're built on estuaries, too.' Of course, the nation's capital is often derided as being a swamp, but its wetlands are home to an incredible diversity of wildlife—including fish, insects, and even newly-arrived large predators, such as coyotes.
But to find fireflies in a city, experts say, it's also important to look for the dark corners where they have the best chance of surviving.
(Will we still see fireflies this summer?) Survival in the city
While it's inspiring that creatures large and small can be resilient enough to still call our cities home, they often do so at great risk.
Many animal species shy away from the bright lights of human-dominated areas, but for fireflies—also called lightning bugs—the problem with lights is more direct.
'Fireflies and glowworm species all use bioluminescent light to court one another. This is how they speak to each other,' says Candace Fallon, senior conservation biologist and firefly lead at the Xerces Society for Invertebrate Conservation. 'When you have a site that's filled with artificial light at levels they didn't evolve with, it can just really have an impact on the productive success of that population.' Common eastern fireflies (Photinus pyralis) are seen at The Battery in New York City, in a composite photograph made from 1,294 one-second exposures. Despite the threat of light pollution, urban green spaces like this one help fireflies continue to thrive.
Imagine being out in the dark and trying to zero in on one specific point of light, says Fallon. Then imagine trying to do the same thing in a world awash with streetlights, billboards, and dusk-to-dawn lights.
Of course, light pollution is just one threat among many.
'When we did our [IUCN] Red List assessment a few years ago, the biggest threats to fireflies were definitely things that impact a lot of other insect and wildlife populations,' says Fallon. 'So, things like habitat loss and degradation, pesticide use, and climate change.'
Unfortunately, there isn't much historical data to contextualize where numbers are today, but most experts remain worried about firefly population declines. While only 150 of the world's 2,600 firefly species have been assessed, scientists say 20 percent of firefly species are threatened with extinction.
Given how important light is to the lightning bug life cycle, one easy way to help wild firefly populations is to turn off outside lights.
'Even simple things like closing your curtains at night so that light isn't spilling out into the habitat outside,' says Fallon.
Another boon is to let patches of lawn grow 'a bit more wild and unruly,' she says. This is because fireflies need moisture and native vegetation.
Finally, reducing pesticide usage can be helpful for insects of all kinds—especially the grub-killing pesticides people use for their lawns.
'Fireflies are beetles, so that can have an impact on their larva,' says Fallon.
If you'd like to get even more involved with firefly conservation, the Xerces Society runs a citizen science project called Firefly Atlas that seeks to get a better grasp on how lightning bug populations are changing.
After all, no matter where these insects are found, they are worth saving.
'Aside from their own intangible value that they have just by existing, I think fireflies serve a really special place in human society,' says Willow. 'They're a portal that connects people to the wonder of the natural world around them.'