Flickering Fireflies

Fireflies, also known as “lightning bugs,” light up the summer evening sky all over Ohio. Fireflies are not simply bugs, nor are they flies—they are soft bodied, winged beetles. Although they look the same to us, there are about 2,000 different species of fireflies!

The firefly’s abdomen is like a tiny, cool-burning light bulb—only better. When the firefly’s light flashes, nearly 100 percent of the energy is given off as light; a typical incandescent electric light bulb only gives off 10 percent light, while the other 90 percent is wasted as heat. Fireflies can turn their lights on and off, and flash their lights in distinct signals.

Nature’s Light Show

The summer evening light shows are performed by male fireflies. As they fly around our backyards, the males flash patterns of light to the females, who perch on blades of grass close to the ground. The females flash back to the males with their own then signals. As this flash dance continues, the male keeps moving closer to the waiting female. Once they find each other, they will mate. Each species of firefly has a different mating signal. The males will not fly down to a female that sends the wrong species signal.

The females of some species have evolved the ability to play a nasty trick. They can mimic the female response flashes of species other than their own. Using this fake flash, they can attract the male of the other species to them. As the unsuspecting male flies down to meet a friendly looking female, he is captured and eaten!

Lightning Bug Life Cycle

Firefly adults are about half an inch long, and have an average lifespan of about two months. Males outnumber the females by about fifty to one. Once the female firefly has mated, she lays her eggs on or under soil. The eggs begin to hatch in four weeks. The eggs and larvae of some firefly species can glow, and are known as “glow worms.”

Fireflies are carnivorous, meaning they eat other insects, such as slugs or worms. The firefly larvae are meat eaters, too. Once hatched, the larvae can catch worms and slugs by injecting them with a numbing fluid. Firefly larvae can even detect a snail or slug slime trail, and follow it to the prey!

Firefly Fireworks

The cool light given off by fireflies during their abdominal flashes is called bioluminescence. Luciferin, a heat resistant substance located inside the firefly’s abdomen, is the source of light. Luciferase, an enzyme also in the abdomen, is the trigger. Oxygen is the fuel, and a common compound found in plant and animal cells, ATP (adenosine triphosphate), converts to energy and causes the luciferin-luciferase mixture to light up.

Scientists are still not sure exactly how fireflies control their lights, but they have found many important uses for the chemicals luciferin and luciferase. Since living cells have ATP and oxygen, researchers can add luciferin and luciferase to detect harmful bacteria in food, milk or water. The two chemicals are also used for special electronic detectors used in spacecraft to look for earth-life forms in outer space! Luciferin and luciferase are also being used in research on human diseases such as cancer, multiple sclerosis, cystic fibrosis, and heart disease. Firefly technology has also been used to produce safer, cold light for flashlights, flares and holiday lights.

Firefly Facts and Fiction

• Ancient Chinese myths explain that blinking fireflies came from burning grass.
• In European legend, a lightning bug flying in the window was a warning that someone was going to die.
• When the Aztecs talked about fireflies, they meant a spark of knowledge in a world of darkness.
• The Native Americans collected lightning bugs and smeared them as decorations on their faces and chest.
• When a firefly is under stress, such as being caught in a spider's web, its taillight glows brightly.
• Although the firefly’s light is meant to find a mate, the shock of a firecracker or thunder may cause a field of fireflies to flash at the same time.

Catch the Firefly Fun!

Male fireflies are easiest to see and catch at dusk, about one hour before the sun goes down. Go outside in a grassy spot, and watch for small flickering lights hovering in the air. Carefully cup your two hands around the firefly, and don’t squeeze! When you hold your palm out flat, the firefly may stick around a little while on your hand until it sees a flash it just can’t resist.

Be sure to catch the nightly firefly light shows, going on now through August at your favorite Ohio State Park! 

Photos from Left to Right: The “glow worm” firefly larvae, en.wikipedia.org; Close-up of the body structure of a firefly, sciencenewsforkids.org; Photo of the safest way to catch a firefly without harming the firefly is by cupping ones hands around the insect; Firefly on leaf, sciencenewsforkids.org.