Every year in North America as spring turns to summer, fireflies emerge in parks, forests and backyards.
But one type of firefly has a unique capability. They blink in unison and are called synchronous fireflies.
They're found in a few places like the Smoky Mountains in Tennessee and the Allegheny National Forest in Pennsylvania.
Their rhythmic displays are magical to observe. They've become a tourist attraction in some places, with festivals and late-night tours.
Scientists know that male fireflies light up to attract females. But they're not sure why these fireflies light up in unison. Some suggest that it's to the fireflies' advantage to cluster and show off their lights in a synchronised display in order to better attract attention from the females.