David Cappaert, Michigan State University, Bugwood.org

Little is known about the luminescent beetles commonly known as fireflies.

On Friday evening, step on out back and count the flashes.

In the second year of a firefly study conducted by the Baruch Institute for Marine and Coastal Sciences, organizers are asking residents to make their own, one-minute backyard counts sometime between 8 and 10 p.m. and report how many they see. The heart of the study takes place during the same hours at Hobcaw Barony, home of the Belle W. Baruch Institute of Coastal Ecology and Forest Science in Georgetown.

Fireflies, or lightning bugs, are luminescent beetles, the magic creatures of childhood. Generation after generation of kids have popped air holes in jar lids to capture them. Overall, the beetles are considered to be in a long decline because of:

--Development of the moist forest-edge grassland habitats where they thrive.

--Artificial-light pollution that disrupts their reproduction because they light up to attract mates.

--The use of fertilizers and mowers on suburban lawns.

But not a lot is known about them. The study is the first real population survey in the South, said Clemson University entomologist J.C. Chong, one of the organizers.

The insects' numbers can vary sharply year to year. Biochemist Alex Chow of the institute counted more than 100,000 in a forest-edge study in 2009. Last winter, the forest underwent a controlled burn and none were counted.

Entomologist Brian Scholtens, a College of Charleston biology professor, isn't so sure the critters are vanishing. He thinks that people are living in more urbanized areas and simply see fewer of them where they live.

"I've always been able to find fireflies if I go to the right places at the right time of year," he said.