Fireflies across the U.S. have seen a robust surge in growth this summer in part to a wetter weather pattern.

But those fiery little critters — which some call lightning bugs — might be in a steady decline.

“Insect populations are known to vary from year to year,” said Eric Berger, a freelance journalist for The Guardian. “A one-year increase is not enough to indicate that there has been a reversal in the downward trajectory of fireflies.”

Berger added that scientists do not have baseline data for firefly species and only recently started to monitor populations.

“A lot of what they're using is anecdotal evidence, but they have started to set up monitoring sites to inventory fireflies so that they can determine whether the population has increased or decreased,” he said.

Of the studies conducted so far, Berger says fireflies face a number of threats from extended periods of drought due to climate change, light pollution, habitat destruction and the use of pesticides.

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