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Lightning beetles light up my life

Lightning beetlesfascinate young people, who often catch them in their hands.

By TIM GIBB - Purdue Extension Service

Possibly the most romantic insect in the world is known for the pulses of soft, amorous light it emits in parks, backyards and roadsides on warm spring and summer evenings.

First, the male flashes its seductive light in a quick Morse love code-like signal while hovering a few feet above the ground. Then, the female replies with her own coy blink, proclaiming her whereabouts in the grass below as a subtle invitation to meet in person. It is romantic courtship in the insect world.

But what are they saying exactly?

Well, it may be something as romantic as “O Romeo, Romeo! Wherefore art thou Romeo?” followed by “Here I am my love! Come to me quickly.”

The lines are familiar to anyone who has read Shakespeare’s romantic tragedy Romeo and Juliet. Juliet utters them as she laments over Romeo’s surname and the feud between their two families – the only thing keeping them apart.

Names have also become a problem in the world of romantic insects. The particular insect I am referring to goes by several names, and no one can agree on which one is correct.

Lightning bugs, or fireflies, or lightning beetles? In fact, there are probably as many different common names given to these as any other insect in the world.

Some of them: lightning bugs, or lightning beetles, or firefly beetles, or glow flies, or golden sparklers, or fire devils, or moon bugs, or big dippers, or blinkies, or flying embers, or little sparks? How about the name peenie wallies? All of these common names are apparently used by someone, sometime, somewhere, for some good reason. But what self-respecting insect would be comfortable being called a peenie wallie?

Harvard linguistics professors in 2003 found that 29.07 percent of Americans surveyed call them lightning bugs, 30.43 percent call them fireflies and 39.91 percent use the two names interchangeably. A disappointing 0.32 percent call them by other names such as glowworms or lightning beetles. Mercifully, only 0.02 percent of Americans call them peenie wallies.

Leaving etymology aside, entomologically speaking, these insects are not worms, flies, or bugs at all. Rather, they are beetles that belong to the insect group or family that insect scientists call Lampyridae. Thus, the proper and most scientifically accepted common name should be Lampyrid, or lightning beetle, and I will henceforth refer to them as such.

The Lampyridae family is composed of more than 2,000 species of lightning beetles. Some are nocturnal and some are not. Only the nocturnal species have the ability to produce light flashes. Most lightning beetles are found in the Midwestern and Eastern states.

Lightning beetles live in various habitats, but most live near heavy vegetation, near large stands of trees, or in agricultural or prairie fields, and you can most often see them flashing in the margins between. They deposit their eggs in the ground near ponds, streams, marshes, rivers, lakes, small depressions that hold water, or near soils that are kept moist. Hatched larvae (called glowworms) feed mostly on worms, snails, and slugs.

Most people do not even notice lightning beetle eggs or larvae until they become adults but they are hard to forget after witnessing the spectacular pyrotechnic lighting displays they create. Flashing beetles are often the target of children who chase and collect them in bottles and watch them light up on their night stands or tables later that night. Lightning beetles mostly feed on flower nectar so are never considered a pest.

The flashes that lightning beetles produce are species-specific communications. They vary in color (yellow, amber, or green) and pattern (in a single or in a series of multiple sparkles like camera flashes). Others appear as a single sustained glow or burn of up to a full second in duration. While flying upwards or in the shape of a letter J, these are reminiscent of children waving glow sticks in the dark. In some places and times, certain lightning beetle species synchronize their flashing such that the whole population flashes together, creating a mesmerizing spectacle – an enchanted, magical, romantic utopia.

As much as we would like to think that the light show is all put on for our pleasure – to beautify our world or entertain our children who chase and capture them on hot summer evenings – the true purpose of the light-producing flashes and patterns is for lightning beetles to find and recognize each other.

It all comes down to sex and romance. Male lightning beetles flash to court females, and female lightning beetles flash to instigate mating.

But even knowing why lightning beetles produce their signature and romantic glow is not always enough to appreciate that they are among only a handful of animals that can actually manufacture or produce light within their own bodies.

The process (called bioluminescence) is a chemical reaction wherein an enzyme called luciferase reacts with a chemical called luciferin in the presence of oxygen. The result of the reaction is the most energy-efficient light in the world – nearly 100 percent of the reaction is emitted as light rather than heat. Compare that to artificial light efficiency – 90 percent in LED, 85 percent in fluorescent and less than 10 percent in incandescent light bulbs. The insect regulates the duration and the intensity of the flash by controlling the size and timing of the bursts of oxygen into the reactions.

Luciferase has proven to be a useful chemical in scientific research, food safety testing and forensic tests. In the past, it was collected by harvesting lightning beetles and then used in the canning or bottling industry to detect whether a bottle was properly sealed. When added inside a bottle, the luciferin would glow in the dark if oxygen entered from the outside – indicating a faulty seal and a potentially spoiled product.

Since their discovery in lightning beetles, luciferin and luciferase have been synthesized and have inspired toys such as glow sticks, LED lights and even some medical tools. They have been used in medical research of multiple sclerosis, cancer and other important medical problems.

So, the next time you see lightning beetles doing their thing on a warm spring or summer evening, remember that their unforgettable displays of bioluminescence and pyrotechnics may not only light up your own life (and possibly inspire personal romantic feelings), but they can also provide a benefit to science.

Just don’t spoil the magic by calling them peenie wallies.

Tim Gibb is a professor of entomology at Purdue University, gibb@purdue.edu.