Mass Gatherings
Thousands of fireflies can make an entire forest flash together
For a short period each year, synchronous fireflies in Great Smoky Mountains National Park coordinate their flashes into one of the strangest nighttime wildlife displays in North America.
Video: National Geographic. Embedded from the original YouTube source.
The mechanism
Why this happens
Male fireflies use species-specific flash patterns during mating, and this species is known for synchronizing repeated flashes and dark intervals.
Season & place
Where this event happens
Great Smoky Mountains National Park, Tennessee · Synchronized mating display. Timing and local conditions can vary from one occurrence to the next, so current local guidance matters when planning around a recurring event.
At first, individual lights flicker randomly in the forest. Then more males join in, the pattern aligns, and entire sections of woods pulse together before dropping back into darkness.
The display has become popular enough that Great Smoky Mountains National Park manages peak viewing through a lottery system to reduce traffic and protect habitat.
What to know
- The display usually occurs during a two- to three-week mating season.
- Peak timing shifts with temperature and soil conditions.
- The National Park Service limits access to protect both the insects and the viewing experience.
If you go
Watch without becoming part of the problem.
Follow local closures and wildlife guidance, keep a responsible distance, avoid blocking migration or access routes, and do not disturb roosts, nesting areas, dens, or concentrated animals for a photo. Conditions and access rules can change quickly.
Good questions
What people usually want to know
Why do synchronous fireflies flash together?
The flashing is part of a mating communication system. Researchers continue to study exactly why synchrony improves the signal, but males align repeated flash patterns during the display.
When can you see synchronous fireflies in the Smokies?
Peak activity usually falls between late May and June, with timing varying by environmental conditions.