A few evenings ago my wife called my attention to what she believes were fireflies in our backyard, but I am not convinced that she correctly identified these insects. The light quality seemed wrong to me and what I saw could have been some other insect species caught briefly in light reflected from the many nearby sources.
"Glowing, glowing, gone!" announces a website about fireflies and my recent experience certainly supports that concern. I find it very sad that so few of today's youngsters can experience the thrill of seeing lightning bugs and even catching them.
A personal memory: when I was only four or five years old, my mother helped me catch a firefly in a mason jar and take it to bed with me. I still recall drifting off to sleep watching the intermittent glowing of that beetle on the table next to my bed. The next morning my mom insisted that I release the firefly, because, she said, "It has to eat to recharge its battery."
Why are fireflies disappearing? No one knows, but there are many hypotheses. We light up the night nowadays and our widespread light pollution may be disrupting their breeding. We spray pesticides to control mosquitoes and spread other poisons on our lawns to kill Japanese beetles, in the process killing beneficial insects like fireflies. Firefly larvae need forest litter and the rotting wood of decaying logs near standing water, sites that are harder to find today. For a time one company organized children into a Firefly Scientists Club to collect and forward thousands of fireflies (at a penny apiece) for its commercial purposes. In the south fire ants prey on fireflies. It is indeed a wonder there are any of them left.
Some terminology: fireflies or lightning bugs are common names for the over 2000 beetle species of the family Lampyridae. Not all of them produce the bioluminescence (biologically produced light) that gives the family its names. Glowworms are the larvae of these beetles and many of them, as their name implies, also produce light. In Europe many glowworms live above ground and are seen at night in gardens; ours, however, live underground so their bioluminescence is rarely observed.
Why do fireflies light up? Certainly not to entertain us. Three purposes are conjectured. First, like several brightly colored insects, they may be identifying themselves as bad-tasting, even poisonous food. "Pass me by," they signal to predators like toads.
Second, their light signals very likely play a role in attracting a mate. In fact, a large firefly species called Photuris is often referred to as the femme fatale firefly. It imitates the signals of females of another species, Photinus. When the male Photinis approaches, it is promptly killed and eaten by Photurus. Hardly the kind of behavior we like to see in our favorite insects.
Finally, their glow may attract tiny midges which serve as food.
And what is it that lights? The light is caused by two (devilish?) chemicals, luciferase and luciferin, that meet in the beetle's abdomen. Firefly light is cold. All the energy goes into the light itself, whereas nine-tenths of the energy of our incandescent and neon bulbs creates heat.
How can you identify firefly species? If you are like me, you ask an entomologist. They use clues like the color of the firefly's light, which ranges from the yellow-green of Photinus and Photuris, although the Photuris is a bit darker; through the yellow-amber of Pyractomena; to the eerie blue or green of the more southern Phausis reticulata.
Firefly flight patterns and the timing of their light flashes differ as well.
A remarkable feature of some fireflies is their synchronized flashing. An entire forest is light then dark then light again with this alternation continuing for hours. Some people travel thousands of miles to Kuala Selangor in Malaysia and similar Asian locals to observe this phenomenon, but there are two places in this country where this is also occasionally seen: near Elkmont, Tennessee in the Great Smoky Mountains and in South Carolina's Congaree National Park.
Am I right about the population decline of our regional fireflies? I invite readers to communicate to me your own experiences with these interesting beetles and how you view their current status.-- Gerry Rising