Dr. Peleg and Dr. Sarfati placed two cameras 13 feet apart on the ground with an overlapping field of vision. Like producers on a movie set, they calibrated the feeds with a checkerboard and an initial artificial light signal. The overlapping footage allowed the researchers to reconstruct a cone-shaped area of the fireflies’ flashes in three dimensions. The researchers also placed two cameras in the middle of the vegetation in an attempt to see the swarm through the eyes of a participating firefly. As their cameras recorded, they waited quietly by the edge of the clearing, watching the ribbons of twinkling lanterns.
The 3-D reconstruction allowed the researchers to characterize several complex patterns in the swarm’s behavior. The male fireflies did not flash instantaneously, but rather in a cascading wave across the swarm. For example, sometimes the flashes would begin at the bottom of the ridge and move toward the insects at the top. This relay-like propagation of flashing suggests that fireflies interact with the swarm locally, taking their cues from the fireflies around them, Dr. Peleg said.
This propagation pattern is also found in other animal swarms such as schools of fish, she added, where local interactions between fish can ripple out to the entire group.
“I see my neighbor is flashing, so I flash as well,” Dr. Sarfati explained.
The reconstruction also revealed that the flashes often occurred in bursts where one flashing firefly on the move would incite other, slower moving insects to flash, too. This observation suggests there is no clear firefly leader or single locus of activity, said Andrew Moiseff, an associate dean for behavioral and life sciences at the University of Connecticut who has researched the Great Smoky’s synchronizing fireflies since the 1990s.
Dr. Moiseff, who advised the researchers, said their findings confirmed what he expected after years in the field. “It’s spectacular,” he said, adding that the 3-D approach had already offered insight into the mechanisms behind the swarm that he had not known how to address in his early research.
Though the new paper offers insights into the flashing swarm, many factors remain unknown, such as how individual fireflies respond to their kin from variable distances or multiple flashes from different individuals, Dr. Peleg said.