In the summer months, adults and children alike marvel at glimmers of light, chasing sparkles and trying to capture their flicker in Mason jars. These glimmers are fireflies, also known as lightning bugs, glowworms or moon bugs. This summer we saw a resurgence of fireflies in southern Wisconsin after their populations declined over the last 10 years.
Why do fireflies glow?
The blinking lights of fireflies so many enjoy serve a real purpose — fireflies communicate by blinking. Males fly around flashing to attract females that hover in the tall grass and blink back. Mating season is June through July, and fireflies are most active between dusk and 10 p.m.
Fireflies have relatively short life spans — some don’t even eat while they’re alive. After mating, fireflies lay eggs in the ground, and those eggs then mature into glowworms. Not all fireflies are bioluminescent, or glow.
As cities grow, greenspaces are paved over or grass is mowed short, destroying natural habitats for firefly mating rituals.
Where have all the fireflies gone?
While 2025 was a peak for this beloved beetle, this was only a pleasant blip and not a sign of firefly population recovery.
“The reason that a lot of people saw a lot more [fireflies] this summer was the fact that we had quite a wet spring and early summer, which meant that a lot of the habitats that were typically not available for larvae were available,” says Dan Young, entomology professor at UW–Madison.
Firefly populations have decreased in Wisconsin and the nation due to habitat loss, pesticide use, light pollution and salt used to melt ice on roads. Additionally, artificial light can interfere with fireflies’ mating patterns.
People can work to protect fireflies by turning off porch lights and floodlights at night, as well as limiting the use of pesticides and herbicides. Climate change also exacerbates all threats through drought and rising sea levels.
“If you like your cute little lights, cool, it’s your thing,” Young says. “But understand that could be having a significant impact on fireflies’ ability to find one another and mate, and it seems like everybody likes fireflies.”
Why is conservation difficult?
Firefly conservation is impaired by the inability to assess how many fireflies there really are.
“Fireflies are extremely taxonomically challenging,” Young says. “We have a hard time understanding what the species are if you look at them anatomically.”
Because of this, researchers don’t have accurate population estimates to track the impact of conservation efforts. There are about 25 species of fireflies identified in Wisconsin, but Young says researchers could end up discovering closer to 30.
Lightning bug lovers can assist scientists by submitting data — photos of fireflies and records of flash patterns — to public, collaborative databases like Firefly Atlas and iNaturalist.
ILLUSTRATIONS BY LENAH HELMKE
Feature photo: Fireflies blink outside of Linggu Temple, a famous Buddhist temple in Nanjing, China. Photo courtesy of 蘇一品/Wikimedia