Synchronous Fireflies in the Great Smoky Mountains

Thousands of Photinus carolinus flashing over a creek in Great Smoky Mountains National Park. Males of this species fire a burst of five to eight flashes, then go dark for about eight seconds, and across a whole hillside they fall into step until the forest seems to pulse. It is still courtship, scaled up: the dark pause may help males pick out a female's answering flash. The display peaks for a couple of weeks, sometime between late May and late June depending on the year, and the park's Elkmont viewing nights are allocated by lottery.