Q: When I moved into our neighborhood forty years ago, there were lots of fireflies. Now they are rarely seen. I have never used pesticides, and would love to re-introduce/re-establish fireflies in my garden. Any ideas or suggestions?
- ---JoAnn in Barrington, RI
- ---Wendy Jones in Eastern North Carolina
Then a recent Associated Press story reporting on a conference in Thailand centered on their dwindling numbers caught my eye. So I called the American researcher quoted in that story, Fredric Vencl, Ph.D., an associate research professor at New York's Stony Brook University and a research associate for the Smithsonian Institution.
A Tropical Biologist, Dr. Vencl was attending the conference because he had discovered a new species of these bio-luminescent wonders on a Panamanian mountain. But he's no stranger to their American cousins. In fact, he began our conversation with the admission that he too had grown up calling them "Lightning Bugs" in his boyhood home of Ohio. Neither term is correct. These fabulous insects aren't flies or bugs, but true beetles, as distinguished by the hard shell covering their wings.
He explains that there are literally thousands of species in the well-named family Lampyridea; and most, if not all, appear to be dwindling in number. The conference dedicated to trying to reverse this disturbing trend was held in Thailand, he explains, because that nation's queen is a huge firefly enthusiast. So the Bright Beetle has at least one friend in a very high place!
In areas outside the US, like that mountain in Panama, the culprit is an old one: Loss of habitat. Luckily, Dr. Vencl and some friends have been able to raise enough money to actually buy the land occupied by his new species and protect it from the logging that threatened to wipe out his find shortly after its discovery.
Here in the States, he cites four main enemies of the fabulous flashers in addition to habitat loss: Pesticides, chemical fertilizers, compulsive landscape neatness, and outdoor lighting.
Because fireflies spend much time near the surface of the soil, they're especially prone to the effects of farm and garden chemicals, including chemical fertilizers, whose high salt content is deadly to the creature's egg and larval stage. And those hungry glowworm larvae are also vulnerable to chemicals picked up by their prey, typically slugs, snails, earthworms and other soft-bodied surface dwellers.
Having a carefully manicured property removes the slightly wild areas they need for mating and breeding. And the same over-the-top outdoor lighting that star-gazers have been bemoaning for years may make the wonderful mating flights of the male impossible for a female waiting down at ground level to see. And vice versa; if the soil line is lit up like a baseball field, the male can't see his invitation being accepted.
For most species here in North America, the life cycle goes like this: Males fly around on summer evenings, flashing their desire for a date with the bio-luminescent appendages in their hinders. Females are down at ground level, on top of a weed or blade of grass, searching the skies for a male whose flash pattern is correct for her species. She responds with her own flashing (especially if his light is especially bright or he can flash it more rapidly or longer than those of his rivals), he flies down and they mate.
She then lays BB-sized round eggs, some of which dimly glow. The creatures that emerge from those eggs definitely glow; that's why their common name is the glowworm. They look a little like pillbugs and sowbugs; and if you're persistent, you may be able to find them down on the ground in damp weedy areas in May down South, and June up here in the North. (Look for their flashing on dark, moonless nights.) The glowworms feed (on your slugs), drop down into the soil to pupate and then emerge as adults in time for the dance of summer to begin anew.
What can gardeners and homeowners do to help insure their survival?
- Don't use chemical fertilizers! Use natural ones, like compost, compost tea and fish and seaweed mixes.
- Don't use toxic chemical pesticides! And don't use broad-spectrum organic pesticides in areas where fireflies live and breed. Species specific organic pest controllers like BTK (which only works against pest caterpillars) and BTI (which only prevents mosquitoes and other biting flies from breeding) are 100% firefly safe; as are insecticidal soap and oil sprays, as these two controls only work when you can see and soak the pest. Just don't spray any lightning bugs!
- Turn off outdoor lighting at mating time. That's between 6:45 pm and midnight from May through August; you'll help the fireflies and get to see them. If lights can't be turned off completely, hook them up to a motion detector, suggests Dr. Vencl. Or replace ones that shine in all directions with low-to-the-ground fixtures that point straight down.
- And leave some weedy, messy areas on your property. Glowworms and their prey are creatures of moisture; they love mucking about in leaf litter and damp areas that are a little bit wild.
- And if your landscape has been getting bone dry in spring and summer, consider putting in a little water feature with some firefly-friendly habitat at its margins. And don't light it! With any luck, those amazing insects will take care of that part for you.