Some of the mathematical mysteries behind how groups of male fireflies match their flashes when they’re clustered closely together have recently been illuminated by a group of scientists at the University of Colorado Boulder who study the blinking of fireflies.
Now, in a follow-up study, the researchers report on additional experiments that shed an even brighter light on fireflies’ synchronous flashing. Of the approximately 130 firefly species in the United States, only three are known to exhibit such synchrony. One of those, Photuris frontalis, is concentrated in protected natural areas in the eastern U.S., such as Congaree National Park in South Carolina where the study authors have witnessed the phenomenon firsthand.
“It’s magical,” marveled computer scientist Orit Peleg in a press release. “At certain times of night, fireflies have a single rhythm for the entire group, and they’re very punctual.”
The research team of computer scientists like Peleg as well as mechanical engineers captured male fireflies from the same old-growth forests where they’d conducted their previous studies, which demonstrated only males synchronize their flashing. Next, the captive males were put in a completely dark tent and exposed to a small LED light flashing at regular intervals.
Read more: “The Mathematical Mysteries of Fireflies”
In nature, these males flash once or twice per second. In the experimental setup, the LED blink rates varied from once per second to as fast as once per 300 milliseconds (about a third of a second).
The male fireflies kept up with the lights—provided that the first LED blink was close in time to their own flash. If the LED light blinked just before the firefly flash, the males rushed their next blinks to catch up, seemingly anticipating that the subsequent LED flash would come sooner. If, conversely, the LED light blinked just after the firefly flash, the males would wait longer to flash again.
Of course, firefly males in the wild would see multiple flashes of other males; still, their ability to keep the beat with the LED teases out a mechanism underlying their ability to synchronize across entire aggregations of fireflies.
From the data, the study authors developed what mathematicians call a “phase-response curve” for the firefly flashes—essentially, a formula that describes how an outside light source drives fireflies to change their own flashing patterns. “This research opens the door to discovering other examples of synchronization in nature that we haven’t seen yet,” explained lead author and computer scientist Owen Martin.
There’s still another mystery to unravel, however: Why the males of some firefly species sync up their flashing in the first place. No matter the amount of flashing lights at the source of that question, the answer remains elusive. 
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Lead image: arthurgphotography / Shutterstock
