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The research team discovered that even a small number of interacting male fireflies can synchronize their flashes, but periodic bursts only occur in groups larger than 15. The flashes were correlated over several meters, indicating long-range interactions characteristic of emergent collective behavior. However, Peleg et al. also observed some individual trajectories, suggesting additional competitive mechanisms may be involved—for example, early flashing fireflies appeared more mobile and flashed longer than those flashing later.
Collective display of Photinus carolinus fireflies recorded in Great Smoky Mountains National Park in early June 2019.
Building on this earlier work, Peleg’s lab conducted field research each May from 2021 to 2025 at Congaree National Park in South Carolina. They set up a pop-up tent isolated from external light sources and exposed captured fireflies to a dim LED light that mimicked firefly flashes, blinking at intervals ranging from once every second to once every 300 milliseconds.
The results showed that fireflies were most likely to adjust their flashing rhythm when the LED blinked nearly, but not exactly, simultaneously with their own flashes. Males would speed up their next flash if the LED blinked just before theirs and delay their next flash if the LED blinked immediately after. The authors likened this behavior to an individual in a crowded concert hall trying to clap in sync with the beat of the audience.
“For an entire season, I spent nearly every night in the dark watching lights blink at a fixed frequency,” said former graduate student and co-author Owen Martin about the field observations. “Then, occasionally, I’d experience the magical moment when a firefly would start syncing with the light. I wondered if I was just imagining it.” Subsequent mathematical analysis confirmed these patterns: the individual flash dynamics followed a phase-response curve, which the authors used to develop an “integrate and fire” model that accurately reproduced the observed synchronized flashing patterns.
DOI: bioRxiv, 2026. 10.64898/2026.01.19.700439 (About DOIs).
