Fire and Lightning
Gray Stanback
Firefly, lightning bug, call them whatever name you want, these insects (actually a type of beetle, but then again, who’s counting?) are an indispensable part of summer across the United States. Children make games out of catching them, and for adults nothing sets the mood for a romantic outdoor dinner like a swarm of glowing fireflies.
A firefly’s light is the result of a chemical reaction inside its body. Two chemicals, luciferin and luciferase are secreted by special organs in the insect’s abdomen, and when they collide they produce a soft yellow light. This light is the most efficient in the world: 100% of the energy used in its creation is converted to light, as opposed to only 10% in a standard light bulb. The fireflies that you see flying about at night are males, who use their lights to attract mates. However, they are not the only ones who glow.
The reactive chemicals that fireflies use to glow have their own practical uses for humans as well: for example, electron detectors built using these chemicals have been used to search for life on other planets as well as to detect food spoilage and crop failure.
Firefly eggs are laid underground and glow with a dim greenish-yellow light. So do the larvae, which are sometimes called glowworms. The glowworms overwinter, then spend about a week as pupae before emerging as adults and flying off to seek mates. Some fireflies, however, are the femme fatales of the insect world. Their males imitate the light signals of other firefly species’ females in order to attract their males. Once the male firefly has gotten close enough, the fake female attacks him and eats him. Other than this, fireflies typically do not eat as adults. Those that do feed mainly on smaller insects, while glowworms live underground and eat worms, slugs, and snails. Fireflies themselves aren’t eaten by very many other animals, since their bodies contain poisonous chemicals.
Fireflies are particularly fond of moist, humid areas, so it’s no surprise that they are especially common this summer, which has been one of the wettest in recent memory. On any given night, one can see several dozen fireflies in a small area while walking down the street in Davidson, twinkling a few feet above the ground like miniature stars.
Unfortunately, fireflies are in trouble. One of the biggest threats to their long-term survival is a phenomenon called “light pollution.” This is what happens when too much artificial light is left on in the middle of the light, which can confuse and disorient nocturnal animals that rely on the stars to navigate. Fireflies are affected too, even though they don’t navigate by the stars. Instead, light pollution blocks out their light signals and makes it difficult for them to find mates and therefore reproduce. Even car headlights can disrupt fireflies’ displays. Synchronous fireflies often go out of synch when a car with its headlights on drives past.
The most obvious thing that can be done about light pollution is to simply not leave too many excess lights on outside at night. Light pollution doesn’t just hurt fireflies, of course; it is also bad for all manner of other animals that rely on the cover of darkness to survive. Furthermore, many insects are attracted to artificial lights, flying close to the light bulbs and killing themselves. Reducing light pollution, then, is not merely an aesthetic decision. It also saves the lives of many animals.
Whether you call them fireflies, lightning bugs, or something else entirely, these fascinating insects are a timeless symbol of the summer months. For the sake of both ourselves and them, we should hope they stay that way. The experience of summer evenings would be very different without them.