Fireflies are soft beetles that belong to the family Lampiridae. There are over 2,000 species around the world and they’re found everywhere except Antarctica. Fireflies (also called lightning bugs) have a special protein in their bellies, a pigment called luciferin. As the insect breathes, air rushes into tubes in abdomen where oxygen reacts with the luciferin. The chemical reaction gives of the glow with which we’re so familiar.
The light a firefly gives off is a cold light and they are the most efficient producers of light on the planet. Nearly 100 percent of the energy produced is light; in a typical light bulb, only 10 percent of the energy is light. The rest is given off as heat. This ability of fireflies has become of special interest for those involved in medical research. Today, scientists can implant the lightning bug’s light-producing gene into cells inside other animals. They can then monitor the glow that’s produced and track those cells in the host’s body. By making cancer cells glow, for instance, researchers can follow the effectiveness of a particular treatment regime. If all of the glowing cells disappear, it’s a good sign the the treatment is working.
In nature, fireflies blink to do one of three things. First, it’s to attract a mate. Males and females of the same species have a particular pattern of flashes that allow them to find each other. Most often the female will be perched on a branch or a leaf of grass while the male flies around showing off his best blinks. When the female recognizes the flashing as coming from a male of her own species, she will answer him with her own specific flashing pattern. As with a lot of females, she tends to select the flashiest male.
Another reason fireflies glow is to avoid being eaten. Lightning bugs have a nasty taste caused by an abundance of a chemical called lucibufagens in their bodies. Once a predator has munched on a firefly, they begin to associate its flash with the bitter taste and tend to avoid eating fireflies again. The one exception to this are toads. The flavor doesn’t seem to bother them at all. In some cases, a toad has been found to have consumed so many fireflies that they glowed themselves. Nonetheless, having lucibufagens is so important for a firefly’s survival that the third reason for flashing has evolved.
Some females of differing species have developed the ability to mimic the response flashes of species other than her own. When a male flies down hoping to meet a nice girl with whom he can raise a family, he finds a mimicking female and winds up being a late night snack instead.
Fireflies live in a variety of environments. They love moisture and often can be found along streams and near ponds. Fireflies spend the winter as larvae buried in the soil and emerge in the early spring to feed. By late spring, lightning bugs have emerged as adults. After mating, the female lays her eggs on the surface or just below the soil line. In about four weeks, the eggs hatch and the larvae begin to feed. The larvae live in the ground and eat earthworms, snails and slugs. Lightning bug young will also scavenge detritus and small dead animals. Some species will even track a snail or slug by following its slime trail. The larvae have sickle-shaped mandibles that they use to hold their prey while they inject a paralyzing venom. The venom not only paralyzes the hapless victim, it also dissolves its tissue, making it easier for the young firefly to consume it. Some species have even been observed attacking a large prey together like a pack of wolves. Most adult fireflies feed on nectar and pollen. Some adults are predaceous and still other species don’t feed at all.
I’m often asked by quite a few people why there are fewer lightning bugs flying around than when they were kids. No one actually counted lightning bugs back then, but most entomologists who study fireflies are concerned that their numbers are on the decline. Some people blame their local mosquito foggers, but they’re not the culprits. We are to blame. Prior to World War II, few people in the U.S. had anything like the yards and lush lawns we have today. After the war, American GIs came back home after having spent a lot of time in Great Britain. They brought back with them the Brit’s love of lawns and gardens and, with the GI Bill allowing almost universal home ownership for the first time, they began to create their own yards. This radically altered the lightning bug’s environment and, coupled with the development and overuse of pesticides, has no doubt been the major cause of the decline in fireflies throughout America.
If you are fortunate enough to have these wonderful creatures in your backyard, grab your kids and a couple of empty jars and go outside and collect a few. It will bring back memories for you and make memories for your kids.
Tim Lockley, an entomologist, is retired from a 30-year career with the U.S. Department of Agriculture as a research scientist. For answers to individual questions, please send a stamped, self-addressed envelope to Tim Lockley, c/o Sun Herald, 205 DeBuys Road, Gulfport, MS 39507.