Fireflies (also called lightning bugs) are beetles. Most of their lifecycle is spent in the larval stage (1-2 years), where they feed on snails, worms, and smaller insects in the leaf litter on the forest floor. Once they mature into the adult form, they only live for about 3-4 weeks and many do not feed.
Scientists studying the synchronous firefly have determined that the males flash in unison as a way for the female to be certain she is responding to one of her kind. There are other firefly species flashing at night, and some of them are predatory, so she must be able to recognize males of her species.
The flash pattern of Photinus carolinus is a series of 5-8 flashes, followed by a pause of about 8 seconds, and then this pattern is repeated. Initially the flashing appears random, but the period of darkness is synchronized. As more males start joining in, the flashing will also begin to synchronize and entire sections of the forest will be pulsating with light.
Timing of the Display
The mating season of Photinus carolinus lasts for approximately 2-3 weeks each year. The dates that they begin to display varies from year to year based on temperature and soil moisture. We use daily temperatures and predicted temperatures to set the dates of the public viewing event, but any natural phenomenon is highly variable and difficult to predict exactly.
As the season begins, a few insects start flashing, then more join the display as the days pass. They reach a peak and then the numbers gradually decline each day until the mating season is over. Since 1993, which is when dates were first recorded, this peak date has occurred at various times from the third week of May to the third week in June.
During the mating season, nightly displays can be affected by environmental factors. For example, fireflies typically won’t flash in heavy rain, but on misty, drippy evenings they will likely still display under the forest canopy. Cool temperatures, below 50º Fahrenheit, will also shut down the display for the night.
Light Show Etiquette
Flashlights disrupt the fireflies and impair people's night vision. The light show is best when you:
You can also help protect the fireflies and their habitat:
Last updated: January 21, 2023