KNOXVILLE, Tenn. (WATE) — Each year thousands come to the mountains to see the synchronous firefly light up the night sky.

Synchronous fireflies, whose scientific name is Photinus carolinus, are one of the many fireflies species that live in Great Smoky Mountains National Park. The species is also one of a few North American species that are known to synchronize their light patterns.

According to the National Park Service, fireflies are beetles. They spend most of their lives as a larva, where they eat on snails, worms and smaller insects from the forest floor. NPS says the larval stage will last for one to two years. As adults, the bugs only live for 3 to 4 weeks and many do not eat during that time. In total fireflies only live for one to two years.

Fireflies gained their name came from their flashing mating displays. The bugs are a good example of bioluminescence, which means light produced by a living organism. Other creatures that produce light include jellyfish, plankton, glowworm beetles, and gnats.

To make their light, fireflies combine the chemical luciferin and oxygen with the enzyme luciferase in their abdomen. This light is a cold light as nearly 100% of the energy is given off as light. The NPS said this is unlike the light from a light bulb where 10% of the energy is light and 90% is heat.

Each firefly species has its own pattern that helps males and females recognize each other. The major of the bugs create a greenish-yellow light, however, others create more blue or white light. The male bugs tend to flash while flying while females tend to be stationary.

According to the NPS, scientists who study the synchronous firefly have determined the males flash in unison to allow females to be certain she is responding to one of their own kind. This is important as some of the other firefly species flashing at night may be predatory.

The flash pattern of Photinus carolinus is a series of 5 to 8 flashes, followed by a pause of about 8 seconds, and then repeated. At the beginning of the display, the flashing appears random but the period of darkness is synchronized. As more males join in, their flashing will begin to synchronize.

Each year, the mating season of Photinus carolinus lasts for around 2 to 3 weeks, which is around the same time the bugs are adults. The exact dates vary from year to year based on the temperatures and soil moisture. The peak time of the season usually takes place between the third week of May to the third week of June. The display can be impacted by a number of factors. For example, the bugs will not flash in heavy rain or temperatures below 50º Fahrenheit.

The NPS uses daily temperatures and predicted temperatures to set the dates for their annual viewing event. Other places where the fireflies display can be seen include Congaree National Park in South Carolina, Allegheny National Forest in Pennsylvania, and Rocky Fork State Park in Unicoi County.