Synchronous fireflies (Photinus carolinus) are one of 14 species of fireflies that live in Great Smoky Mountains National Park. They are the only species in America whose individuals can synchronize their flashing light patterns.

Fireflies (also called lightning bugs) are beetles. They take from one to two years to mature from larvae, but will live as adults for only about 21 days. Their light patterns are part of the adulthood mating display. Each species of firefly has characteristic flash pattern that helps its male and female individuals recognize each other. Most species produce a greenish-yellow light; one species has a bluish light. The males fly and flash and the usually stationary females respond with a flash. Peak flashing for synchronous fireflies in the park is normally within a two-week period in mid-June.

The production of light by living organisms is called bioluminescence. Many species of insects and marine creatures are capable of it. Fireflies combine the chemical luciferin and oxygen with the enzyme luciferase in their lanterns (part of their abdomens) to make light. The chemical reaction is very efficient and produces little or no heat.

No one is sure why the fireflies flash synchronously. Competition between males may be one reason: they all want to be the first to flash. Or perhaps if the males all flash together they have a better chance of being noticed, and the females can make better comparisons. The fireflies do not always flash in unison. They may flash in waves across hillsides, and at other times will flash randomly. Synchrony occurs in short bursts that end with abrupt periods of darkness.

Light Show Etiquette
Flashlights disrupt the fireflies and impair people's night vision. The light show is best when you:

• Cover your flashlight with red or blue cellophane.
• Use your flashlight only when walking to your viewing spot.
• Point your flashlight at the ground.
• Turn off your flashlight when you find your viewing spot.

You can also help protect the fireflies and their habitat:

• Do not catch the fireflies.
• Stay on the trail at all times.
• Pack out all of your garbage.