Blue Ridge Naturalist: Firefly Lights Dimming

Winter Fireflies are usually found on the bark of a tree, but the author has found them inside wooden bird boxes in late winter and, as seen here, on the wooden siding of her carport wall in spring. Photo: Marlene A. Condon.

While a student at Virginia Tech, I lived in the area all year long. In summer, when the majority of students were gone, the town of Blacksburg was peaceful and quiet.  It was especially delightful to live there at that time of the year.

One of my favorite summer memories is of spending time at night on the Tech Drill Field in July, the height of firefly season. The world was a better place then; no streetlamps lit the pathways crossing the field as they do now. After dark, this big open area was a purely magical place to be.

Sitting on the ground, you were surrounded by the biological lights of uncountable fireflies. It was enchanting and every bit as wondrous as seeing the gazillion stars twinkling in the night sky from a very dark location on the Earth.

But just as those stars have dimmed from human view, thanks to the manmade lighting that overwhelms our eyes’ ability to see them, so too are firefly lights dimming, thanks in part to that same artificial lighting that interferes with the ability of many wildlife species to reproduce successfully.

It saddens me deeply to read report after report of fireflies disappearing around the globe, yet I do have hope for their salvation. When folks were alerted to the diminishing numbers of the Monarch butterfly, in large part because of the loss of milkweed plants for their caterpillars to feed upon, people really rallied for the cause and planted milkweed in gardens and along roadways.

Indeed, we may be already witnessing the success of these efforts. In the fall of 2016 it was easy to discern that there had been a tremendous increase in the population of Monarchs. For the first time in years, I watched butterfly after butterfly flutter across the sky over my yard as Monarchs made their way south in September.

And at Virginia hawkwatch sites, they were seen in good numbers just about every day since the watches began in late August (the same time Monarchs start leaving North America). As evidenced by the assistance offered to Monarchs, when people know what’s wrong with a situation, many will do what’s right to fix it.

If you want to assist fireflies, a good resource is Silent Sparks: The Wondrous World of Fireflies by Sara Lewis. Published by Princeton Press in 2016, this book is up to date on the current situation.

Written by a scientist who is very much a firefly enthusiast, the prose is friendly and understandable, not dry and stuffy (full of technical jargon) as you might expect from a researcher.

Her goal is to share the collective knowledge that scientists have gained over the past thirty years and also to persuade folks to step outside and enjoy these “silent sparks.” You’ll learn such things as how a firefly produces its light, the details of firefly courtship and mating, and the chemical defenses employed by these insects to discourage predators from eating them.

Along the way, you’ll read about unusual scientists, such as the late Cornell entomologist, Tom Eisner, who created the research field of chemical ecology to find out how insects use chemicals to protect themselves. He became the world’s leading chemical ecologist by sometimes nibbling as well as smelling insects!

You will also discover that fireflies are a main attraction to tourists in certain areas of the world where they still congregate in numbers large enough to produce “dazzling displays.” Eighty thousand tourists a year visit Malaysia and 90,000 visit Taiwan for firefly-viewing tours during the appropriate season.

And much to my surprise, 30,000 tourists visit the Great Smoky Mountains National Park during the two weeks in June when synchronous fireflies put on their own special light show, something I had never heard about.

Synchronous fireflies emit their glow simultaneously. Each insect flashes at the same time as the others, and then every one of them goes dark for a certain amount of time until the group again flashes all at the same time. This kind of firefly wasn’t known to exist in the United States until it was finally brought to the attention of scientists in 1993.

A woman who had grown up watching these insects in Tennessee with her family contacted a scientist who had just returned from Southeast Asia. He had gone there to study the synchronous fireflies of that area.

As can be frustratingly typical of scientists, the biologist from Georgia Southern University was skeptical at first. But he and a colleague visited that summer to see for themselves the natural spectacle. This yearly display had been enjoyed by generations of local families—until they were “politely but firmly” escorted from their cabins on what had become national park land in 1940.

Perhaps the most important section in this book is Chapter 8, “Lights Out for Fireflies?” Here you’re told about the myriad things people do that negatively impact firefly populations, giving you the insight you need in order to help these creatures that seem like they belong in a fantasy.

Habitat protection is at the top of the list. Development of natural areas really takes a toll. Because adult fireflies do not travel very far from where they spent their lives maturing, a breeding population can easily disappear when people destroy the marshes, meadows, and woodlands where these insects breed.

However, folks could preserve firefly habitat around their homes by reevaluating whether they really need such things as a built-in swimming pool that may not be used very often, an “outdoor room” that would invariably lead to the killing of wildlife that does not understand the concept of “off-limits,” and a nature-unfriendly lawn that encourages the loss of precious groundwater.

Another threat to fireflies (and many other kinds of wildlife) is the overabundance of light that humans surround themselves with unnecessarily. When you are out at night, take note of the gas stations that seem to be more brightly lit than when the Sun is shining! Note the houses with outdoor lights fully illuminating them even though passersby do not need the view.

These lights are not harmless. They interfere with fireflies trying to communicate via an otherworldly-colored glow that cannot possibly compete with man’s artificial lighting. The starry sky has virtually disappeared from urban, suburban, and even many rural areas nowadays due to light pollution. We should not allow our fireflies to likewise disappear.

If you are looking for a gift idea this holiday season, Silent Sparks is a hard-covered book that is fascinating, informative, and entertaining. You might even consider purchasing a copy for your local library. Those silent sparks need our help if we want to avoid having their glow permanently extinguished.


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