FIREFLIES' spectacular back-yard light shows are an indelible summer memory for people of all ages. It's one of those simple pleasures that doesn't ever seem to fade. You can even share the pleasure across generations -- a rarity if you house adolescents. The scientific name for the firefly's flashy talent is bioluminescence. The ability to glow is found in fungi and bacteria, in some plants and animals that live in the oceans and in the insect family. The spook wood of East Coast legend is really bioluminescent fungus glowing with satisfaction as it digests dead timber. Pliny the Elder, one of the earliest naturalists, documented a clam that had a glowing siphon and could emit a phosphorescent stream of liquid when frightened. His discovery launched a fad among Roman yuppies when they learned that eating the clam would make one's mouth phosphorescent for a short period. Glow-in-the-dark banquets became the rage. (You can imagine what Caligula did with that one.) Unraveling the mystery of nature's glowing oddities kept scientists searching from Pliny's time until the 1950s, when William McElroy, a biologist at Johns Hopkins University, put the final pieces into the puzzle. McElroy enlisted the help of Maryland youngsters in his research. Child volunteers were given nets and a bounty of 25 cents per 100 fireflies turned in to McElroy. As many as 800,000 fireflies were collected during a summer. The names of the hapless grad students who counted the catch are not recorded. Previous research had pinpointed the substances in the firefly's posterior that combine to produce its cold green light -- luciferin, luciferase and oxygen. But nobody could figure out how the bugs switched their lights off and on. McElroy found the substance that acts as the switch and also located the biochemical energy source -- adenosine triphosphate, or ATP -- that allows the firefly to emit light without heat. West Coast people may have Hollywood and star-studded affairs, but only those of us east of the Rockies grow up with lightning bugs. (West of the Rockies adult fireflies don't flash, they glow on the ground in the larva stage.) The flashing lights we see on summer nights are the adults performing a gaudy mating display. The males are the airborne flashers, while the females (many without wings) demurely flash from the grass. Each species has its own code that leads the searching lovers to each other. While we may think our home-grown variety is spectacular, other parts of the country and the world can claim a clear superiority. In Florida and Texas, what the natives call fireflies are really luminescent click beetles. These guys have a light so intense that only four beetles placed in a jar will produce enough light to read by. In Southeast Asia, male fireflies congregate by the thousands in trees and flash their light in perfect synchrony. In Japan, fireflies are raised by dealers to be sold for the yearly Firefly Festival on Lake Biwa near Kyoto. Festival-goers row out on the lake by the hundreds and at a signal release the fireflies all at once. When your children want to collect fireflies in the back yard, try luring the males to you by turning a small flashlight off and on. Wait a few seconds between bursts and keep the flashlight face down in the grass. Although we didn't have the patience to stay with it for very long when we tried this, we did seem to get some of the critters to fly lower and in our general vicinity. However, nobody cruised in close to ask for a date. (Along with the fireflies, we have a bumper crop of mosquitos this year. Liberally apply bug repellent before embarking on a firefly chase.) When you have collected the evening's quota, try putting the fireflies in a glass jar and placing the jar in warm water (their light should intensify) and then in cold (their light should dim). Don't submerge the jar in your enthusiasm as we did, because fireflies are definitely not aquatic. Capture equipment should be shatterproof. A good bug container can be easily assembled from two tuna or cat food cans with one end removed from each. Cut a rectangle from screening with a width of about eight inches and a length equal to the circumference of one can plus two inches. Tape all sides of the screen with masking or duct tape and then roll it into a cylinder the size of the cans. Put the cans on either end of the cylinder, with one can serving as a removable lid. If somebody falls while catching the bugs, there will be no shattered glass to worry about. An added benefit of this kind of a container is the availability of oxygen. Lightning bugs use a lot of oxygen to produce their light and a glass jar with holes in the lid will quickly smother them. If your kids are normal and want to take their bug collection to bed as a natural night light, this contraption will keep them glowing longer. However, if your kids also have a penchant for naming all living things (we caught Bud -- later named Bud Light -- Twinkle and Joey), you may be able to persuade them to release their catch. You don't need to worry about stuffing grass in the jar for the bugs. They don't eat anything as adults except an occasional sip of nectar. Their only adult ambition is to find the proper mate. Once that has been achieved and some eggs laid, the adults die. Fireflies take one to two years to reach adulthood, but their prime time is short:They begin to appear in mid-June, and by the end of July they have found their heart's desire, satisfied their reason for being and turned out the lights.