January 27, 2023

As dusk deepens the shadows at the edge of the forest, a small beacon illuminates the darkness. Soon the dusk is full of floating lights, each winking a message in a peculiar semaphore: “Man seeks woman for short-term commitment.” This courtship takes place on summer evenings around the world among beetles of the family Lampyridae, commonly known as fireflies.

However, the darkness in which fireflies have always chased their liaisons has been broken by the glare of artificial light. The love affair of people with enlightenment has led too many of the Earth’s habitable surfaces suffer from light pollution at night. In recent years, scientists who study fireflies have heard of people fearing the insects are in decline, said Avalon Owens, an entomologist at Tufts University.

“There is a sense of doom. They don’t seem to be in places where they used to be,” she said.

So little is known about how fireflies live that it’s difficult to assess whether they are endangered — and if so, why, said Dr. Owens. But in a study published Wednesday in the journal Royal Society Open Science, she and Sara Lewis, a professor of biology at Tufts University, shone some light on how fireflies respond to artificial lighting. Experiments in forests and fields, as well as in the lab, showed that while some North American fireflies mate with wild abandon regardless of the lighting, others failed to complete any successful mating under the glare of the lights.

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