The pinpoint of green in the driveway gravel stopped me in my tracks. I'd just rolled the trash toter up the hill to the roadside for the morning's pickup, and was on my way back down to the cottage when I thought I saw a tiny gleam.
At first I wondered whether it might have been a bit of glass or metal foil reflecting some light source. But what light? There'd been a thick cloud cover all day, and the low overcast had stayed around, wrapping the night in an extra-deep cloak of darkness. Any hint of moon or stars had been blotted out. I could barely make out the white areas of Moon the dog's fur from five feet away. A thick screen of leafy trees and brushy undergrowth blocked the back door's weak porch light from reaching the slope of the drive.
Had I simply imagined the green?
No, there it was again—though not quite where I thought it had been the first time. Then I saw another glimmer of green a few yards away…and a third, just the merest hint, coming from the grass bordering the drive. I thought then the light's maker had to be some sort of bioluminescent insect. Curious to know more, I retrieved a flashlight from the cottage and returned to the hillside.
Lightening bugs aren't the only insects around sporting bioluminescence—that ability to generate light by mixing chemicals in their body. While fireflies are beetles which belong to the family Lampyridae, another group of bioluminescent beetles belong to the family Phengodidae, the glow-worm beetles. I wanted to catch a specimen of whatever was giving me an emerald wink, have a close look, and maybe try and key the insect down to see what I'd found.
One thing for sure, whatever they were their gleam wasn't nearly as bright as the flash from a typical backyard lightening bug. Even given the intense darkness, you had to be within a few yards to see one emit its brief glow. Their light was soft and green—a green the shade of a fresh lime, or the tips of certain spruce needles in the spring. Plus the miniscule light was often partially obscured by a blade or grass or some other bit of debris. It took a minute or two to located a glow I could quick-follow to the source with the flashlight's bright beam.
Eventually I captured my prey—several, in fact. The creatures, while identical in appearance, did vary slightly in length—ranging from about 12mm to possibly 20mm. They were quite active and would crawl across the palm of my hand in a moment. I put them in an empty pill bottle and took them to the desk for further research.
I still don't know—at the specie level—exactly what I have, but I do know they are firefly larvae. They began life as an egg, deposited on or slightly below the surface of the ground, by the winged female adult a few days after mating; doubtless the offspring of a pair of those dancing lightening bugs that twinkled like fallen stars over the yard's lawn and bushes on summer evenings. Three or four weeks after laying, the eggs hatched into this larval stage.
Firefly larvae feed all summer and into the warmer weeks of autumn, before burrowing underground or beneath a bit of tree bark where they'll overwinter until spring. From what I've read, firefly larvae are predators, preying on small animals such as snails and slugs.
After making a few (not particularly good) photos, I returned the captured firefly larvae back to their chosen hunting territory and sent them on their way. Once my eyes had readjusted to the night, I stood for another quarter-hour, watching, as all around the brethren of my captured larvae turned their muted neon-green lamps on and off…tiny bioluminescence embers burning amid the rich darkness of the changing season.
