Firefly season is here: When to watch for summer’s flashing lights

A new map shows when the Big Dipper Firefly is most active across the central and eastern U.S., while conservation biologist Richard Joyce explains how people can help protect firefly habitats.

For many people, the glow of fireflies marks the heart of summer, but the timing of those displays depends heavily on location, weather, habitat and species.

AccuWeather built a map with Global Biodiversity Information Facility data to highlight the timing of the Big Dipper Firefly, Photinus pyralis, across the central and eastern United States, where sightings are most common during June, July and August. The species is one of the most familiar backyard fireflies in the country, making it useful for comparing the start and peak of firefly season across different regions.

Richard Joyce, a conservation biologist with the Xerces Society, said focusing on a single species is important because the timing of fireflies can vary dramatically.

“There are a lot of different species of fireflies,” Joyce said. “A lot of people think of the Northeast ... but they're everywhere.”

Joyce said the Big Dipper Firefly is a good species to track because it is widespread, with records from the Florida Panhandle and Texas northward into states such as Michigan. However, it is not found everywhere. Joyce noted that it is missing from parts of northern New England, including Massachusetts.

Not all fireflies follow the same summer calendar. In some parts of the Southeast, Joyce said, certain firefly species are active much earlier, with some appearing in March and April and finishing their season by mid-May.

For the Big Dipper Firefly, observations compiled through biodiversity databases and community science platforms show activity building through early summer, peaking in many areas during June and July and continuing into August in some locations.

Joyce said public observations have helped scientists better understand where fireflies are found and when they are active. The Xerces Society works with community scientists who observe flash patterns, photograph fireflies and share location details that help researchers identify species without killing or collecting them.

“Those two pieces of getting a photo and getting flash pattern details will help us identify the species,” Joyce said.

Creating a backyard habitat to welcome fireflies

Fireflies may be a familiar part of summer, but Joyce said many people are surprised to learn how diverse they are. The U.S. has more than 170 named species of fireflies, and up to one-third may face an elevated extinction threat. Some states have dozens of species, including around 50 in Florida alone.

The insects also face several threats tied to the way people manage yards and landscapes. Light pollution is one of the biggest concerns because many fireflies rely on flashing signals to find mates.

“Light pollution can interfere with their reproduction and their survival,” Joyce said. “These are nocturnal insects that for, you know, as long as they've been on Earth, the brightest thing that they've dealt with was the full moon.”

Moisture is another key factor. Fireflies are beetles, but Joyce said they dry out more easily than many other beetles. Short grass, removed leaves and cleared fallen branches can strip away the damp, sheltered places fireflies need.

“They really love moisture,” Joyce said. “They love moisture and the things that they eat as larvae also love moisture.”

Those larvae live in the soil and leaf litter, feeding on soft-bodied creatures such as earthworms, slugs and snails. Joyce said fireflies can live up to two years, meaning drought or poor habitat conditions during one season could affect the number of adults seen much later.

Good habitat can help buffer fireflies from dry conditions. Joyce said wetlands, fallen logs and layers of leaf litter can create “little pockets of moisture” that act as a lifeline.

Homeowners who want to make their yards more firefly-friendly can start by leaving some natural areas in place. Allowing leaves to remain under trees and shrubs, reducing unnecessary mowing, keeping parts of the yard darker at night and avoiding pesticides can all help create a better environment for fireflies.

Joyce said firefly conservation often begins at the household level, with people managing their yards for lightning bugs and using yard signs to explain why leaves or logs have been left in place.

He also emphasized that fireflies need habitat year-round, not just during the weeks when adults are flashing.

“Fireflies didn't go anywhere,” Joyce said. “They're even (there) in the dead of winter ... they are needing, a place to live and things to eat pretty much year-round.”

That means protecting fireflies requires thinking beyond the glowing adults of summer. The insects spend much of their lives out of sight, hidden in leaf litter, soil and moist habitats.

The glow itself is not limited to the adults people see blinking above lawns. Joyce said all firefly larvae in the U.S. are believed to glow, even though not all adult fireflies do.

As the Big Dipper Firefly season unfolds, Joyce said one of the most important things people can do is recognize that the familiar flashes in their yards are part of a much larger and more fragile diversity of species.

“We're really trying to do is make sure we keep that full, full diversity of fireflies,” Joyce said.

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