Wet spring leads to a summer of fireflies | Lexington Herald Leader

Children: Prepare your jars and poke holes in the lids. Adults: Get ready to stand in awe.

Monday is the first official day of summer, but it comes in the middle of a season you're not likely to see on your calendar:

It's lightning-bug time in the Bluegrass.

And, as a lot of people already have noticed, it's one of the best and brightest years for the glowing insects.

Lee Townsend, a University of Kentucky extension entomologist, said he and his colleagues have been hearing for several years from people who thought the number of lightning bugs has been in decline.

Not this year.

"I've noticed more just in our yard, and I think the numbers are up," Townsend said.

The reasons aren't exactly clear.

Lightning bugs, also known as fireflies, are predators — their diet includes slugs, earthworms and snails — and the number of lightning bugs is likely to increase as their prey increases, Townsend said.

Moisture also appears to be a factor in lightning-bug populations, he said. Just as our wet spring has brought swarms of mosquitoes, it has graced the night air with countless small trails of light.

And lots of sex.

That's what this flashing business is all about, Townsend said. It is a kind of "mate location device."

"It's males who are flying and flashing to attract a female," he said. "Females typically are sitting on the ground, and they will respond to the flash of a male."

Scientists have found that different species of lightning bugs — and there are many — have different flash patterns. They also have found that, within species, females tend to find the flashes of some males to be "sexier" than the flashes of others. You probably have to be a female lightning bug to understand.

Marc Branham, a University of Florida entomologist who is one of about 20 people in the world who study lightning bugs full-time (he calls them fireflies), says the flashing started as a defense mechanism.

Lightning bugs taste bad, he said, and the flashing originally warned potential predators that they were about to get a bitter mouthful. It later developed into a mating system.

Branham said he can drive by a field of lightning bugs and identify the species without stopping his car.

In a few places, including several spots in Asia and Elkmont, Tenn., in Great Smoky Mountains National Park, there are species of lightning bugs that flash in unison.

There are 15 species of lightning bugs in Kentucky and 146 in North America, Branham said. Worldwide, 2,000 species have been named, but Branham said another 2,000 have yet to be identified.

The larvae live for a year, but the adults live only a few weeks. In Kentucky, the light show lasts about eight weeks, mostly in June and July. This year, Townsend said, he started seeing them in May.

Lightning bugs produce light by mixing two chemicals — luciferase and luciferin. It produces a "cold light," which means all the energy used goes to creating light and not heat.

There used to be money in them thar bugs: For years, children and sometimes whole families made a little extra money by catching lighting bugs and selling them for a penny each to a company called Sigma Chemical (now Sigma-Aldrich).

The company used the bugs for medical research because the chemical reaction that causes the glow also can be used to identify some cancers.

But a company spokeswoman said Friday that it no longer is in the bug-buying business because those chemicals can be made synthetically now.

The glow sticks that children play with today use the same process and are the product of early lightning-bug research, Branham said.

Some scientists say pollution, such as pesticides, and artificial light are causing a reduction in lightning bugs. Like Townsend, Branham said he had been getting reports of fewer lighting bugs for several years — until this year.

"It's kind of a mystery" why numbers appear to be up, he said, adding that because there are no long-term census numbers, it is difficult to identify trends.

To increase the number of lightning bugs in your back yard, experts advise turning off outside lights, letting logs and litter accumulate to provide hiding places, creating water features and, most important, stopping or reducing the use of chemicals.

Lightning bugs are people-friendly. They don't bite or sting. They sometimes hover at low levels, so even little kids can grab them. If you're lucky, you can get one to sit on the back of your hand for a few moments for a close-up light show.