Summer is a time for traditional activities, including picnics, water sports, camping and stargazing. I fondly recall soft evenings when you could romp in the grass barefoot, playing a late game of tag and begging Mom for ice cream cones or s’mores. We always kept a couple glass jars with screw-on lids handy in case our favorite bugs showed up. (Not the mosquitoes!) Right around dusk we could see the first flashes of light moving around the shrubs and flower gardens.
We were chasing lightning bugs, those tiny creatures that flash a soft green or blue light as they slowly fly around in search of love. On a good night, if there was little wind and no rain, we could see hundreds of the insects floating and soaring around us. If you grew up in Maine or on the West Coast, you probably called them fireflies, but names like candlefly, lampbug and moonbug are also used. These delicate creatures are found in many parts of the temperate and tropical world. In places like Europe they are called glowworms.
By any name, these delicate creatures are soft-bodied beetles, with more than 2,000 species identified so far, most of them capable of emitting light. The light is produced by a process known as bioluminescence, caused by the interaction of the compound luciferin with an enzyme called luciferase in the presence of oxygen. There are dozens of natural biological processes for bioluminescence in a variety of creatures — also popular are the tiny dinoflagellates that light up the ocean at night in places like famous Mosquito Bay in Vieques, Puerto Rico. Bioluminescence has also been harnessed for use in medical science.
The lightning bugs you spot in evening flight are generally males, covering ground and flashing light from their abdomens in hopes of spotting an encouraging light from a female in the grass below. Each insect has its own pattern for light signals, with the color, number and duration of flashes, as well as the pauses between flashes, indicating its species. Evolution played a role here in that the light also serves as a warning that the lightning bug carries a mildly toxic steroid that is noxious to many, but not all, predators. Some males end up tangled in spiderwebs and the spiders have no trouble ingesting these tiny snacks. Certain female lightning bugs even use a false light signal to lure in males of other species so the females can dine on the hapless lover boys.
Once the male finds a willing female, he must quickly approach her for breeding. Often, he must fend off other males, pushing and shoving with head, horns and feet, since the population contains relatively few females relative to the number of males. Mating itself can extend for hours as the male tries to prevent other males from getting in on the action in what scientists have termed “copulatory mate guarding.” A few days after mating, the female lays her fertilized eggs on or just below the surface of the ground, where the larvae will spend the long months until the following breeding season.
Lightning bugs are ancient creatures, with their remains having been identified in fossilized amber nearly 100 million years old. But human civilization has not been kind to these fragile creatures, and many species are now at risk of extinction. Draining and filling of wetlands has a significant impact on the ability of these beetles to breed, feed and survive during their larval stages. The conversion of open spaces to housing developments or industrial parks eliminates important habitat. Light pollution from buildings can disrupt courtship signaling and interfere with larval dispersal. As with many other insects, there is growing concern about the heavy usage of pesticides for agriculture and lawn care.
Mankind has long recognized the delicate beauty of lightning bugs and their courtship displays are fascinating to children and adults alike. The insects have been revered in many cultures, with the Japanese creating special parks for celebrating the summer flights of fireflies. In my lifetime I have noticed a significant decline in the number of fireflies seen during a summer evening. Our challenge is to protect and preserve wildlife habitat so that children may always experience the joy of watching these tiny flashes of light in the night sky.
