Lightening Bugs and Their Language of Light
LIGHTENING BUGS AND THEIR LANGUAGE OF LIGHT
Written by Kristine Manganelli (Somerset County 4-H Coordinator)
Adult Lightening Bug
Around here the weather seems to transition into summer by the end of May, perfect for a camp fire and for spotting the first lightning bugs of the season! Those blinking lights in the dark night define summer for me. Observing the light show in my own back yard is magical and mesmerizing. It has me wondering how and why lightning bugs put on this display?
While here in New Jersey we refer to them as lightning bugs, in many parts of the country they are known as fireflies. With more than 2,000 species, lightning bugs are found on every continent except Antarctica. They thrive in warm, humid weather, coming out for the summer in our temperate climate. Lightning bugs live in meadows, and forests, near moist environments such as ponds, streams, and vernal pools. It turns out they are not really bugs or flies at all, they are beetles.
Like other beetles, lightning bugs undergo metamorphosis and complete a lifecycle consisting of four stages: egg, larva, pupa and adult. In mid-summer adult females lay their eggs in moist, wooded areas near soil or leaf litter. Once hatched the larvae will live underground through winter. The rest of a lightning bug’s lifespan is rather short; the other stages only lasting up to three weeks each. Pupation occurs as the weather gets warmer, and shortly after the adults can be seen flying.
Similar to monarch butterflies, lightning bugs are poisonous. Their glow may have evolved to serve as a defense mechanism; a warning to would-be predators of toxicity. Lightning bug eggs and larvae also glow for this reason. If attacked, lightning bugs will shed drops of blood that contain bitter tasting poisonous chemicals in a process called “reflex bleeding.”
Millions of years later, the lightning bugs evolved to use their glow as a means of communication as well. The adults only live long enough to fulfill their sole purpose of continuing the species into the next generation. During this time, light is used as language for lightning bugs, especially when it comes to attracting mates.
In the evening, males flash their light while flying in “courtship signals,” witnessed by females surveying their options from the ground nearby. If interested, the female will blink in response, starting a flash dialogue. Each species has its own specific “flash fingerprint.” Some flash only once or in timed pulses, some flash while shaking their abdomen from side to side, and some flash while flying in patterns that resemble the letter “J.”
Lightening Bugs at Night
In a rare phenomenon, some lightning bugs even blink in synchronicity. Each year hundreds of people travel to the Great Smoky Mountains National Park in Tennessee to observe Elkmont fireflies, the only species in North America capable of lighting up in unison. However, some species cannot light up at all. In fact, there are very few lightning bugs that glow West of the Rocky Mountains. I feel lucky that the species found in our area will compete with hundreds of other males each night to impress potential mates in a spectacular dance.
Lightning bugs put on these performances using a process called bioluminescence – they convert chemical energy into light. A chemical reaction takes place between oxygen and luciferin molecules found in the “lantern” or photic organ inside the lightning bug’s abdomen. Scientists only recently discovered what makes this possible-- a superoxide anion-- a form of molecular oxygen that contains an extra electron. Superoxide anions may be the key to how other bioluminescent creatures’ glow.
Lightning bugs generate cold light, a light so efficient that 100% of the energy goes to producing light rather than heat. This is an extremely rare adaptation as most light sources waste energy through heat. It is still not fully understood how fireflies create their courtship signals, but they may be able to flash by controlling mitochondria oxygen consumption.
Do you love watching lightning bugs as much as I do? You can identify the species of lightning bug in your yard by observing the unique blinking patterns you see and using this inforgraphic.
Unfortunately, due to habitat loss and light pollution, the lightning bug population is in decline. Light pollution comes from man-made sources, and can have a disruptive effect on nature. Lightning bugs are particularly sensitive to light pollution because it obscures their courtship signals. If light pollution prevents them from deciphering the blinking messages, they will not mate, and their species will be at risk of fading away. A simple way to encourage lightning bugs to your yard, is to limit the amount of lights you keep on outside your home each evening. You can also choose to leave leaf piles or dead logs in your yard to create habitat where lightning bugs prefer to lay their eggs.
Catching lightning bugs is fun if done properly using these tips.
If you are interested in contributing to the research and conservation (protection) of fireflies, get involved with Firefly Watch, a citizen science opportunity through Mass Audubon and Tufts University. Citizen Science is the collection of data by members of the general public in a collaborative effort with professional scientists. Anyone in North America can participate by spending at least ten minutes once a week observing lightning bugs in your backyard. All sightings, or even absence of sightings, are valuable scientific data!