- The Washington Times - Tuesday, May 13, 2003

As a child — like many before and after him — Jim Lloyd was fascinated by fireflies but couldn’t figure out why they lit

up and what made it happen.

Now, however, the 70-year-old professor of entomology at the University of Florida can answer that question — and frequently does when children across the nation send him letters, often in envelopes addressed only: “Fireflies,” University of Florida, Gainesville.

“They use [the light] for mate-seeking, but there are some females who seem to use it for landing, too,” Mr. Lloyd says.

It also can be used to lure prey and act as a defense mechanism as the light is used to camouflage the firefly.

It turns out that the approximately 2,000 different species of fireflies use their flashing light in different ways.

The male Photinus pyralis, the species of these flying beetles most common in the mid-Atlantic area, uses a flash every four seconds to attract the female, says Abner Lall, a professor of biology at Howard University who has been doing research on fireflies for 30 years.

“After about one or one and a half seconds, the female responds with one short flash,” Mr. Lall says.

The male Photinus pyralis can tell the flash is coming from a female of the same species by the delay in the female’s response. Males of other species might produce double or triple flashes, and the females might wait a longer or shorter time to respond. The norm for the females, independent of species, is to flash only once, Mr. Lall says. (A sequence of flashes, therefore, would have the male flash, say, three times, the female respond with one flash, the male go through another sequence of flashes, and the female answer with another single flash.)

Another species-specific characteristic is the flight and flash pattern. The Photinus pyralis male flies and flashes in “J” formations.

The color of the flash also is different depending on the species. Fireflies that are out at dusk have a light yellow flash, while those out a little later at night have a greenish flash. Locally, the Photinus pyralis gives off the yellow flash and can thus be seen at dusk, while Photinus versicolor gives off a greenish flash and can be seen later at night.

The flashing — or flirting — goes on for a bit, until the female decides that this is her guy. Both female and male flash until the actual mating starts, and, well, the lights go out.

“But there is another twist in the male and female courtship,” Mr. Lall says. “Have you heard of the femme fatales?”

Mr. Lall is not talking about Lauren Bacall or any other classic movie actress. The femme fatale of the firefly world is way more lethal.

“The femme fatale — after having mated — attracts another male and eats him,” Mr. Lall says.

By feasting on a fellow firefly, the female makes sure her offspring get what they need in terms of nutrients.

A chemical process

The fireflies’ flashes are created through a complex chemical process that has nothing to do with electricity.

The chemical reaction takes place when oxygen interacts with a molecule called luciferin, an enzyme called luciferase and a molecule called ATP, Mr. Lloyd says.

This emission of light by any living organism, such as fireflies, certain fish and bacteria, is referred to as bioluminescence.

Just before the firefly flashes, be it for mating, luring prey, defense or landing purposes, its central nervous system sends an impulse to let in oxygen, which reacts with the chemical compounds.

Scientists are and have been working on adapting the chemical process in man-made technologies. It is used already in medicine when diagnosing certain bacterial infections, Mr. Lloyd says.

There is still more to learn.

“Nature certainly has a lot of secrets that we can learn from,” says Gary Hevel, an entomologist at Smithsonian’s National Museum of Natural History. “The firefly flashes is one of them. … Imagine having a light that sustains itself in a tunnel or in a mine. It would be pretty convenient,” Mr. Hevel says.

One of the most commonly seen human adaptations of bioluminescence is glow sticks, the kind often sold at amusement parks and rock concerts.

To see the chemical reaction at work in nature, Mr. Lloyd recommends visiting any stretch along the Potomac River or taking a trip to Point of Rocks, Md., near Frederick.

The best time to catch a firefly show is in June, July and August, but some may be out flashing already in May.

Males in this area usually fly higher than females, which usually are settled in bushes or on the ground. In other areas of the world, fireflies don’t actually fly around, Mr. Lall says. In desert areas, for example, they often live in termite mounds.

“The termite mounds are lit up like apartment buildings in Manhattan,” he says.

Beetle full of complexity

Fireflies spend most of their lives as babies, or larvae, while their adult life is very short, just a few weeks in some species, Mr. Lloyd says. The larval phase can last for a year.

“It’s a high-risk occupation to fly around,” Mr. Lloyd says of the short adult life span.

Everything from rain storms to spider webs threatens the fireflies’ existence, he says. Other threats include human sprawl.

“They seem to be very habitat-sensitive,” Mr. Lloyd says, “and we’re taking up more and more space, and we’ve lowered the water table, which affects them.”

Just as migratory birds get confused by cell-phone towers and high-rises, fireflies can be confused by light from human activity, too, he says.

Mr. Lloyd says the greatest threat is not that all fireflies may disappear because of increasingly unfriendly environments, but that some species, perhaps ones scientists haven’t cataloged yet, will become extinct.

About 125 species have been named in the United States, and Mr. Lloyd is getting ready to name an additional 30 to 40 based on his research.

It may not seem a big deal to some for a few bugs to disappear, but Mr. Lloyd doesn’t take it lightly because these little creatures, most less than an inch in length, still hold unresolved mysteries: How do they perceive color? Are there other ways they use their flashes?

Fireflies continue to capture the interest of scientists and children alike with their behavior and biochemical capabilities.

“Fireflies are so complex, you can’t even believe it,” Mr. Lall says. “We keep discovering new things about them.”

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