In the first weeks of June, visitors to the Great Smoky Mountains in eastern Tennessee, USA, are treated to a rare natural spectacle, in which thousands of fireflies blink in unison, as if it were Christmas lights shining at night. The species responsible for the performance is Photinus carolinus, one of the few in the world known to synchronize its flash patterns, within a tenth of a second of each other.
These fireflies are actually winged beetles that use bioluminescence during twilight to attract their “mates.”. The light is produced in the lower abdomen, where the insects combine the chemical luciferin with the enzyme luciferase in the presence of magnesium and oxygen ions to produce light. Fireflies are extremely efficient at what they do. Almost 100% of the energy produced in the chemical reaction is converted into light. For comparison, an incandescent bulb converts only 10% of the energy in light, being the rest, 90%, given off in the form of heat. Due to the absence of heat, the light produced by fireflies is called “cold light”.
Fireflies were originally thought to use their flickering light to warn other members of the presence of predators and other dangers. However, it is now known that fireflies light up to communicate with each other.
In some species, the males fly around the females, flashing a very specific pattern looking for a mate, while the females themselves remain fixed on the ground or in the trees and bushes, waiting to produce a flash. Chen the female firefly “likes what she sees,” she responds with a unique flash.
For most fireflies, everything is chaotic, with each male turning on and off at different times, each doing their best to impress. In synchronous fireflies, such as Photinus carolinus, the courtship ritual is more organized. All the males seem to have come to an agreement to flash a unique pattern in unison.. For Photinus carolinus, the pattern is a series of five to eight flashes of yellow light, followed by an eight to ten second period of darkness.
Researchers believe that fireflies synchronize their blinking to allow females to clearly spot the right males.. It also allows the male seeking a female to use the synchronized dark period between flashes to respond. Synchronized flashing therefore reduces visual clutter and helps both females and males find each other.
Synchronous fireflies are quite common along riverbanks in the Southeast Asian jungles of Malaysia and the Philippiness, where they mate throughout the year. In the Western Hemisphere, in the Great Smoky Mountains, the mating period is very short, lasting about two weeks each year.