Photinus carolinus fireflies are famous for their synchronous display. Individual males emit flash trains consisting generally of 5 to 7 flashes every 0.5s (approximately). Swarming males adjust the timing of their phrases on each other's tempo, thus collectively producing periodic bursts of synchronized flashes. P. carolinus populations are found primarily scattered along the Appalachian chain of the Eastern United States, notably in the Smoky Mountains. There, while observed by local residents since at least the 1960s, this spectacular phenomenon started being investigated with modern data collection techniques in the 1990s.

Starting in 2019, we have used high-resolution stereoscopic videography to capture the collective display of Photinus carolinus fireflies in their natural habitat, namely the Elkmont, Tennessee area of Great Smoky Mountains National Park. In this dataset, we provide the three-dimensional (3D), time-resolved coordinates of flash occurrences for several swarming events.

The 3D data correspond to: 1) recordings made every night between June 3 and June 13, 2020 (except June 4 and June 6), at the exact same location in a small forest clearing; 2) recordings made using 360-degree cameras on June 9, 10 and 13, 2020 at two nearby sites. In addition, we are providing a complete set of the original movies for June 11, 2020.

The dataset provided was the basis to the findings presented in: Sarfati et al., Self-organization in natural swarms of Photinus carolinus fireflies, Science Advances, abg9259 (2021). We hope that it will foster further discoveries.

Recordings from June 3 to June 13, 2020:
Two Sony α7R4 cameras were placed about 4m apart in a small forest clearing. The same area with the same field of view was recorded on each night, starting at 9:15pm EST. The raw movies are available for June 11 (the cameras automatically create a second movie after 100min of recording). Camera settings: 60 frames per second (fps); exposure time 1/60s; maximum aperture (f/1.8); maximum ISO (32,000); and focus to infinity. Spatial calibration was performed using several pictures of a checkerboard (25 mm square side length) and the MATLAB stereo calibration toolbox. Flash positions in each frame were extracted by pixel intensity thresholding. 3D coordinates of recorded flashes were triangulated based on camera pose using MATLAB's triangulate function. About 60% of the flashes recorded in each camera could be triangulated. Outlier points (about 1%), for example those falling out of physical range, were removed in postprocessing.

Recordings using 360-degree cameras:
Two GoPro Fusion 360-degree cameras recording at 30 fps were placed on the ground at a set distance (0.9 or 1.8 m) facing the same direction. The cameras were started at around 9:30 p.m. EST (Eastern Standard Time) each night at two different locations. They recorded for about 100 min. 

.MP4 files can be opened with any standard video player
.csv files can be opened with any standard CSV reader
.mat structure files should be opened with MATLAB