City Lights Are Keeping Fireflies From Having Enough Sex to Avoid Extinction


Feb 5, 2020


Image Credit: Tsuneaki Hiramatsu

Who likes sex with the lights on every time? Not fireflies: Urban light pollution reflected by the atmosphere to penetrate even rural wildernesses is getting in the way of fireflies’ reproduction, putting them at risk of going extinct.

This excess artificial light outshines fireflies’ mating signals. Male fireflies keep their tails lit when looking for a partner, while female fireflies respond with their interest via patterned flickers — but the insects aren’t able to spot each other amid the glare.

It’s one of several threats to the survival of the more than 2,000 firefly species globally, according to a new study published in the academic journal BioScience. In the South Asia region, which includes India and Sri Lanka, the biggest threat to firefly survival is habitat loss, such as the disappearing mangrove forests around Mumbai. Fireflies are particularly vulnerable to habitat loss, as “… they need special conditions to complete their life cycle,” lead researcher Sara M. Lewis, a biology professor at Tufts University in the U.S., told the New York Times.

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Additional threats to fireflies in South Asia include light pollution, pesticide use, water pollution, and tourism, like the Pune-area firefly festival, which garnered criticism from ecologists last year.

“It’s not just about spotting the fireflies, it’s about photographing them,” wildlife researcher Dharmaraj Patil told the Times of India in May 2019. “Normally, insects are very delicate and get affected by the flashes. Even a simple walk in the forest can cause some disturbance to the numerous insects on the forest floor.”

While not classified as endangered yet, fireflies “are being lost steadily,” the study’s co-author Michael Reed, a biology professor at Tufts University, told the New York Times.

The gradual loss of fireflies comes amid a broader decline in insect populations globally that could leave the world with more pests and fewer pollinators, both of which outcomes could threaten food supplies. And no less importantly — leave the world with a little less light and wonder.


Written By Liesl Goecker

Liesl Goecker is The Swaddle’s managing editor.

  1. This Family We Love

    With threats to their colonies ranging from light pollution to habitat destruction, Malaysia is at risk of losing its firefly colonies and their symphony of lights forever.


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