Nature's Nightlights

AMC Pinkham Notch Visitor Center

Every night along the river banks of Southeast Asia, the darkness is interrupted by flashes from tiny bugs illuminating the night in unison. It’s no wonder that these insects are known more commonly as “fireflies” or “lightning bugs”. Here in North America, it is much less common for these insects to synchronize their flashes, but that does not keep them from awakening the curiosity of a night-owl naturalist!

Fireflies are a type of beetle notorious for their ability to emit and control flashes of light in a phenomenon known as bioluminescence. Unlike other bioluminescent organisms such as certain species of mushrooms and plankton, fireflies are able to control the timing and frequency of their luminescence for the purpose of communication.

There are roughly 2000 species of fireflies, several of which are diurnal or active during the day. Not surprisingly, these species do not have a flash signal. On the other hand, each nocturnal species has its own unique pattern of flashing to find and attract mates. While adults of most species do not eat, biologists have observed females of the genus Photuris mimicking the luminescent repertoire of other species to attract males for a tasty treat.

The bioluminescent reaction takes place at the tip of the abdomen in specialized cells called photocyte cells. These cells are adjacent to reflector cells which help to project and intensify the light. Few details are known about the chemical process that produces the flashing light, but scientists do know that this process is extremely efficient! The conversion of chemical energy to light energy in a firefly is 98% efficient with only 2% of the energy lost as heat. Compare that to a standard incandescent light bulb which is only 3% efficient, with 97% of its energy lost as heat!

Fireflies are easily observed in New Hampshire on mild summer evenings after sunset in moist areas such as meadows, fields, and open woods. To study these insects up close and personal, all you need is a jar with a lid. By looking closely, you may even be able to distinguish individual species by differences in the color of light and series of flashes. And for those of you ambitious naturalists out there, creating your own bioluminescent light bulb as strong as a reading lamp is quite simple. You only need to capture roughly 25,000 specimens and hope that they blink in unison. (And just as you would turn off your lamp before bed, be sure to release your captives when you are done.)

Picture Credit: Bruce Marlin