Dr. Peleg and Dr. Sarfati placed two cameras 13 feet apart on the ground with an overlapping field of view. Like producers on a film set, they calibrated the feeds with a chessboard 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 to view the swarm through the eyes of a participating firefly. While their cameras recorded, they waited quietly at the edge of the clearing, watching the ribbons of twinkling lanterns.
The 3-D reconstruction enabled the researchers to characterize several complex patterns in the behavior of the swarm. The male fireflies did not flash immediately, but in a cascading wave over the swarm. For example, the lightning sometimes started at the bottom of the ridge and moved towards the insects above. This relay-like spread of the blinking suggests that fireflies are interacting locally with the swarm, taking their cues from the fireflies around them, said Dr. Peleg.
This spreading pattern is also found in other schools of animals such as schools of fish, she added, where local interactions between the fish can radiate to the entire group.
“I see my neighbor blinking, so I blink too,” explained Dr. Sarfati.
The reconstruction also found that the lightning flashes often occurred in bursts, with a blinking firefly in motion stimulating other, slower moving insects to flash as well. That observation suggests that there is neither a clear leader of fireflies nor a single place of activity, said Andrew Moiseff, an assistant dean of behavioral and life sciences at the University of Connecticut who has been researching the synchronizing fireflies of the Great Smoky since the 1990s .
Dr. Moiseff, who advised the researchers, said their results confirmed what he had expected after years in the field. “It’s spectacular,” he said, adding that the 3-D approach had already given insights into the mechanisms behind the swarm that he didn’t know how to address in his early research.
Although the new paper offers glimpses of the blinking swarm, many factors remain unknown, such as: For example, how individual fireflies react to their relatives from different distances or multiple lightning bolts from different people, said Dr. Peleg.