Phosphorescent Fireflies, Luminescent Lightning Bugs

As a favorite sign of spring, hearing peepers barely beats seeing the first fireflies. Last night I returned home after dark and decided to sit out on the porch for awhile and enjoy the breeze. I’m glad I did, because before long I noticed on-and-off flashes of a firefly. Soon I spotted a few more.

fireflyCall them fireflies, lightning bugs or Photuris pennsyvanica, if you must. Either way, childhood fascination with this insect never seems to go away. At Brown County State Park, an exhibit on Indiana’s state symbols invites visitors to vote for their choice for State Insect. Along with the honeybee, fireflies and lightning bugs are always the top picks.

People often find insects creepy. Lightning bugs are the exception. Even kids afraid of the dark will happily run around on a summer evening, catching fireflies to put in a jar. The soft glow of these insect-powered flashlights makes children feel safe outdoors at night — a time usually spent in the glow of a television or computer screen. I doubt the fireflies will remember much of their shared adventure after being set free, but I know the bugnappers will.

These insects have very descriptive (if inaccurate) names, since they are neither bugs nor flies. Maybe we should call them “Blinking Beetles” because they are beetles. The males produce the moving flashes of light we see — the females stay on the ground guiding the males to them with responding blinks. Sometimes the larvae (and even the eggs) may be luminescent.

With over 100 species of fireflies, how do you tell them apart? If you’re a lightning bug, you consult your built-in stop watch and look for flashes with a certain rhythm or timing. Humans need to consult a good field guide or entomologist, but these sources still can’t explain how (or why) hundreds of fireflies will often start blinking in unison.

Lightning bugs are the original compact fluorescents, and we could learn a lot from them about energy efficiency. 90 percent of the energy they use to make the glow produces visible light. Incandescent light bulbs are just the opposite. Only 10 percent of the energy is converted to light — the rest is unneeded heat.

Fireflies are also unknowing partners in medical research. Luciferin and luciferase, the chemicals that produce that yellow-green glow, are being used by scientists to learn more about multiple sclerosis, cystic fibrosis, and other diseases.

Can these little blinking beetles end the energy crisis and rid the world of cancer and heart disease? I don’t know, but they’re sure setting a good example. The evening light show is not put on for our benefit — we just enjoy it from the sidelines (or porch). But as they create light, fireflies are also creating happy memories for us — of warm and carefree evenings spent bonding with bugs. As I sat watching them fly closer and closer to their mates, I felt almost as close to nature as a kid with a jarful of fireflies.

Davie Kean is the master gardener at the T.C. Steele State Historic Site.