Why Are We Seeing So Many Fireflies in New York This Year?

There have been reports of higher than normal firefly populations, but it’s probably fine.

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Jul 2 2017, 3:00pm

Image: Mike Lewinski/Flickr

The other evening I sat in Manhattan's Christopher Park, enjoying a "salty pimp" from Big Gay Ice Cream with a friend, and listening to an intoxicated man rant incoherently on the bench beside us. It was the perfect New York summer night.

Suddenly, all around us, tiny fireflies started to blink into life, and as the sun set the whole park was awash with the luminescent beetles. The next night, I saw them again, floating around some trees a few blocks away. I've lived in Manhattan for three years and have never seen a single firefly. What gives?

"I've been getting reports—over Twitter and email—from all over that firefly populations are booming this summer," said Sara Lewis, a biologist at Tufts University who studies fireflies and wrote a book about them. "I'm glad to hear about the swarms in the West Village!"

Lewis told me these reports are just anecdotal, but that there could be a slight uptick in lightning bug populations this year due to some peculiarities of the insect's' life cycle.

"As juveniles, they spend 1-2 years living underground, then emerge as adults for only a few weeks," Lewis explained over email. "They need moisture during every one of their life stages. So I think it's likely that the firefly blossoming we've all been enjoying is due to the wet spring we had earlier this year."

In the park, I caught a firefly to inspect it, and it looked to me like a big dipper firefly, or Photinus pyralis. It turns out that is the most common firefly species in New York, so it's not all that surprising to have swarms of them in late June. Maybe it was just me?

So I phoned Gabriel Willow, an urban naturalist who works with the New York City Audubon, to see if he'd noticed anything. When I reached him, he was leading a nature hike in the Adirondacks and literally caught a firefly to show the group while we were talking.

"To be honest, I've never not seen fireflies in Manhattan," Willow told me.

He suggested maybe I just had a newfound appreciation for nature, but as a science reporter and a country kid, I wholeheartedly rejected this notion. Willow conceded there can definitely be subtle variances in population from year to year, and some recent changes in New York may have made it a little more hospitable to the eye-catching bugs.

"On a local level, they could be increasing because there's more green space, like Brooklyn Bridge Park and the Westside Greenway," Willow said. "There's also been a real emphasis in recent years in native planting. I imagine as you have more native plants, it might create better habitat for them."

Overall though, firefly populations have been in decline across North America for decades, possibly due to light pollution or the overuse of pesticides. So if you too are finding swarms of them outside your door for the first time, enjoy them.

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