Above the Waterline: Where have all the fireflies gone?

Do you remember the fireflies of your childhood summers?

More than 50 years later, I can close my eyes and recall everything about those humid southern nights: the excitement of running after the blinking bugs with a glass jar (holes punched in the lid), the buzzing of cicadas, crickets and katydids in the background (an iconic southern sound) and the contrast of the tiny lights in my yard with the stars in the sky.

In early June, I joined hundreds of people in a dark hardwood forest near Elkmont in the Great Smoky Mountains National Park to view the light show put on by Photinus carolinus, the only firefly species in America whose individuals can synchronize their flashing light patterns in mesmerizing displays. Elkmont has the largest population in the country, attracting thousands of people every year during the 10-day period when the fireflies flash in their mating ritual.

We walked into the woods, not far from the soothing sound of Jake’s Creek, and put our folding chairs in a small opening. We waited, our eyes adjusting to the darkening forest as the stars emerged above.

Like clockwork, at 9:30 p.m., the firefly performance began: a few flashes at first that built over a half an hour to waves of twinkling lights, one of the most amazing forms of communication in the insect world. It was truly magical; I felt like a child again.

The production of light by living organisms is called bioluminescence – a chemical reaction that combines the chemical luciferin and oxygen with the enzyme luciferase in the firefly’s abdomen. One of the most efficient lights in the world, 100 percent of the energy emitted by the firefly is light. Because the human eye is very sensitive to light in the yellow-green spectrum, the blink of a firefly appears extremely bright, although it represents the equivalent of only .0025 candlepower.

The late, great writer Edward Abbey described the phenomenon more succinctly and poetically as “organic lanterns afloat on the currents of evening.”

Flying four to five feet above the forest floor, several male fireflies flash first to start a group burst; this signal is followed by four to eight synchronous flashes that can be seen throughout the forest as all the insects join in the display. Then abrupt darkness, until the females, resting on the ground blink twice in response to the performance above them. As a male approaches a female, a close range mating dialogue of alternating, aimed flashes begins.

Fireflies are disappearing all over the world, apparently from the destruction, degradation and fragmentation of their habitats as human development spreads. People along the Mae Klong River in Thailand say that a generation ago the flashing insects were so thick in the trees along the riverbank that they served as highway beacons for boatsmen at night.

Here at home, a summer doesn’t pass without my hearing someone lament the fact that the lightning bugs of their youth have largely disappeared.

Scientists don’t know a great deal about these luminous insects because they only began studying them in earnest in recent decades; however, they blame the disappearance on two primary factors: development and light pollution. Logging, pollution and increased use of pesticides may also contribute to destroying firefly habitat.

Human light pollution interrupts firefly flash patterns, according to researchers. Lights from homes, cars, stores and streetlights can make it difficult for fireflies to signal each other during mating, meaning fewer firefly larvae are born next season.

You can help university researchers answer important questions about fireflies and develop programs to save them through a citizen science project called Firefly Watch created by the Museum of Science in Boston. It takes just 10 minutes each week to watch your yard or a nearby park, record your observations and submit the data.

Given Atlanta’s proximity to the Smokies (just a four-hour drive), consider planning your own trip to Elkmont next year. I promise: it will bring back childhood memories and much more.

WHAT YOU CAN DO

Join Firefly Watch at legacy.mos.org/fireflywatch
At Home:

• Turn off outside lights at night.
• Let logs and litter accumulate.
• Create water features.
• Avoid use of pesticides.
• Use natural fertilizer.
• Don’t over-mow your lawn.