It's a childhood memory that many of us possess: Sitting on a front stoop as day turns to dusk, watching and waiting for the flash, flash, flash of fireflies to fill the summer night. But now those beacons in the dark that we captured in mason jars are relatively few and far between, and in some communities seem to have disappeared entirely. Sadly, today's youth rarely encounters these bioluminescent creatures; fireflies are about as familiar to them as drive-in movie theaters, penny candy and the ice cream man. Although concrete information is limited, there's plenty of anecdotal evidence that suggests fireflies are on the decline, and both entomologists and casual admirers are quietly concerned.
In the United States, fireflies are most commonly found in the eastern half of the country, usually near ponds, streams and other areas prone to retaining moisture. Despite the fact that the firefly is the official state insect of Pennsylvania they are arguably most prevalent in the south, owing to the warm and humid weather. James L. Lloyd, a professor of entomology at the University of Florida who specializes in fireflies, moved to Gainesville in the 1960s specifically because of the variety and quantity of fireflies found there. "But many of those species I haven't seen in ten or 15 years. So as a guess, without any hard data, I'd have to say they are decreasing,” he says.
With fireflies seemingly less common than ever before, it's no surprise that misconceptions about them abound. To begin with, fireflies are not really flies at all. In fact, what we call fireflies, lightning bugs or glowworms are actually beetles in the family Lampyridae, found on every continent except Antarctica, with 200-plus species in North America. “Most people don't realize there's more than one species,” laments Lloyd. “They also don't know that you can tell different species apart by their flashing . . . or that the adults of many species don't have light.”
For those fireflies that retain the ability to emit light into adulthood, the flashing—anything from a single flash to a multi-pulse to a constant glow—has a purpose, akin to humans getting dressed up for a night on the town. “The basic reason [fireflies flash] is the same reason people dress up with low necklines and sideburns and all the rest. It has to do with sex,” says Lloyd, who discusses the state of fireflies in a periodic newsletter, The Firefly Companion.
However, long before adults begin flashing to attract the opposite sex, they do so to deter their natural enemies. All known firefly larvae are capable of throwing light and entomologists believe the pulses serve as a warning signal to potential predators that they contain defensive chemicals—in effect, advertising that they are unpalatable. “There are deadly poisons in some fireflies. There have been cases where people fed fireflies to their pet lizards and it killed them,” notes Lloyd, who has some firsthand experience with their bitter taste. “One time my hands were full and when I caught another firefly I had to stick it in my mouth. Boy, it tasted terrible,” he says.
The most common reason given for the decline of fireflies is that suburban sprawl is eradicating wetlands and destroying their natural habitat. “In addition to loss of land, we've lowered water tables,” says Lloyd, “which means water doesn't percolate to the surface and produce little streams, marshes and wet areas. Those are the kinds of situations where many species occur.”
But researchers have also speculated that the amount of artificial light used by humans may be playing a role in holding down firefly populations, as ambient light inevitably interferes with their ability to find mates. In other words, it's almost impossible for a one-inch beetle's tiny tail lantern to compete with yard lights, streetlights and headlights. Not surprisingly, chemical pollution and climatic changes have also been identified as contributing factors.
Ironically, while the long-term prognosis for fireflies looks bleak, the chemicals they use to make light—luciferin and luciferase (combined with adenosine triphosphate and oxygen)—are playing an increasingly important role in medical and scientific research. In the 1950s, researchers confirmed that the light from fireflies creates virtually no heat. Today, scientists are working to transfer the genes associated with light production into places where they don't occur naturally. “They did this with a dog's leg [at the University of Michigan],” marvels Lloyd. “When they perfused the leg with the right kind of chemical the leg lit up. It was kind of fantastic.”
At the same time, some Lampyridae lovers are focusing their attention on raising public awareness about the plight of fireflies, even offering suggestions on how to improve the odds of an encounter. On the Web site The Firefly Files (sponsored by the Museum of Biological Diversity at Ohio State University), Dr. Marc Branham, an entomologist at the American Museum of Natural History in New York, suggests that using fewer chemicals on your lawn and reducing any “extra lighting” on your property may increase the chances of attracting fireflies to your yard.
Meanwhile, Donald Ray Burger, an attorney in Texas who specializes in personal injury law and commercial litigation, has devoted much of his spare time to bringing fireflies back to Houston, lending a significant chunk of his personal Web site to the cause. Since starting the site in 1996 he has received correspondence from firefly lovers around the world—some users sending him information about firefly sightings, others lamenting how they don't see fireflies as often as they used to. “I am encouraged that they are still found just about everywhere,” says Burger. “The sad thing is that it's an exceptional event when people see fireflies now.”
Initially, Burger hoped that his Web presence would help him find someone willing to sell firefly larvae, but that hasn't panned out. As for Houston, Burger says he has personally seen fireflies as near as 30 miles from the city. “I get scattered reports of people seeing them in Houston, but not enough to impress anyone,” he says.
If fireflies ever approach extinction it's difficult to say what impact their absence might have on the environment and the world as a whole. With scientists now able to artificially synthesize the firefly's light producing enzymes, their importance might be more spiritual and symbolic than anything else. According to Burger, the people who e-mail him are already pained about their decline. “I think what people miss is being able to show them to their kids. Fireflies don't do anything but put a smile on your face.”