To some people they’re lightning bugs, to others, fireflies. For Dr. Sara Lewis, they’re silent sparks illuminating the early summer night sky.
On a personal and professional quest to better understand the amazing science behind lightning bug luminescence, Lewis, a biology professor at Tufts University and author of Silent Sparks: The Wondrous World of Fireflies, is among a growing number of academics, citizen scientists, and others striving to help people preserve what are not flies at all but winged beetles, to keep their lovely light alive for future generations.
“All insects serve as essential links in the cycle of life,” Lewis said. “But beyond their ecological function as important predators of snails and slugs, fireflies fulfill our real human need for beauty and wonder. The first time you see the smile on kids’ faces after encountering these magical creatures, you understand just how incredibly they enrich our lives.”
But like so many other creatures, they are currently under threat from several common components of modern life; among them, habitat destruction, light pollution and pesticides. Though these issues are pervasive and far reaching, there are simple practices home gardeners can adapt to play a role in helping create safer firefly havens.
The lightning bug most likely to be encountered on Delmarva is the big dipper firefly (Photinus pyralis), “the species most people think of when they think of lightning bugs,” according to Candace Fallon, senior conservation biologist with the Xerxes Society for Invertebrate Conservation’s Endangered Species Program. But Delaware and Maryland are home to over 25 different species, several of which appear to be threatened, she noted.
The Mid-Atlantic has been identified as a priority conservation area for fireflies.
Endangered varieties include the mysterious lantern firefly (Photuris mysticalamps), keel necked firefly (Pyractomena ecostato), and belted firefly (Photuris pensylvanica), also a newly described species, Photuris eliza, known only from freshwater peat wetlands on the Peninsula,” she mentioned, crediting Delaware State University Professor Dr. Christopher Heckscher and the late Dr. James Lloyd with supplying much crucial research in this area. For those wanting to learn more, Fallon recommended Xerxes’ publication State of the Fireflies.
Fireflies are found on every continent except Antarctica. In some parts of the world they’re more correctly referred to as glow-worms because ground-based females light up to attract males. Here, it’s primarily flying adult males who do the glowing to catch a mating female’s eye. Nevertheless, a critical part of their life cycle is terrestrial and almost invisible; they can spend up to two years developing as larvae on or under the ground, Lewis noted.
The Xerxes Society for Invertebrate Conservation, most often associated with butterflies, has also been prolific in providing insight into helping fireflies survive. Fallon has identified several ways to help attract and preserve them.
“Home gardeners can create firefly-friendly yards by providing an assortment of native plants, leaving some yard areas wild, eliminating the use of pesticides, and reducing artificial light at night,” Fallon recommended.
“Moisture is especially important to fireflies throughout their life cycle, and vegetation can help maintain this moisture in the landscape. Plants are also crucial because trees, shrubs, forbs and grasses provide places to signal, perch and shelter; some species even nectar on flowers or sap,” she added.
While its often in a gardener’s nature to tidy up, Fallon points out that fireflies, like a plethora of other native wildlife and insects, find an unkempt space more hospitable.
“Try letting the grass grow a little taller instead of mowing it down, hold back on removing downed logs and leaf litter. These microhabitat features provide protected spaces vital for fireflies to reproduce, overwinter, and hunt for prey,” she noted.
“Pesticides should be avoided if possible since they can directly affect fireflies or their prey and may degrade their habitat,” Fallon said. “Dark skies are also vital to fireflies — light pollution has been shown to affect their crucial courtship behavior. By turning off outdoor lights at night or installing timers or motion detectors, gardeners help ensure fireflies can communicate with each other to procreate.”
Lewis agreed that gardeners should avoid spraying broad spectrum insecticides preemptively, choosing organic or the least toxic solution applied topically as needed. For outdoor lighting, use the dimmest possible bulbs you can find, and cover them up with a red filter or gel, red being the least disruptive color for fireflies.
Shari Wilson, former head of the Maryland Department of the Environment, recently posted some pointers for firefly fans in her blog, Nuts for Natives. Noting that experts suggest adding a water feature to the garden, Wilson addressed the related issue of mosquitos.
Choosing a water feature with running water will help discourage mosquito larva from breeding, she noted. Her own home yard, which has become a neighborhood attraction due to the number of fireflies visiting there, has two small bird baths fitted with aquarium pumps which keep the water continually moving, plus a small pond with continuously recycling water. For standing water she advised adding mosquito dunks which have been recommended by Dr. Doug Tallamy, University of Delaware entomology and wildlife ecology professor. The dunks are nonharmful to birds and pets and located at hardware stores and garden centers.
Fallon also urged gardeners to be vigilant in limiting mosquito breeding opportunities. “Routinely check to make sure there is no standing water in plant pots, kiddie pools, buckets or rain gutters. Fix leaky water hoses and address any other areas where water may be pooling unnaturally. If you have a bird bath, change the water out frequently.
The idea of creating community firefly sanctuaries has begun to grow. In Greenbelt, Md., citizens presented the idea to community leaders, who brought the idea to fruition with the Greenbelt Firefly Sanctuary in February 2020, just before the first Coronovirus Pandemic lockdown began.
“Out of concern for the decline of firefly species, a group of residents living nearby produced a report and recommendation to the city council to name that parcel of land a Firefly Sanctuary,” according to Greenbelt Environmental Coordinator Kevin Carpenter-Driscoll.
The response has been overwhelmingly positive, with groups bringing lawn chairs nightly to catch the “show”, a nice distraction, especially during the pandemic, Carpenter-Driscoll noted.
“To help maintain the sanctuary area, the city has prohibited the use of pesticides and herbicides in the area, and has established a soft border around the edge, keeping grasses long for most of the year and mowing at the end of winter. We have also been working with volunteer groups to remove invasive plant species and establish native plants that will help to increase biodiversity in the area,” he added.
For more information:
• Texas nonprofit Firefly Research and Conservation recently started a new habitat certification program (
• Two Xerxes publications provide other helpful tips for firefly-friendly landscapes, including Firefly conservation guidelines at, plus Fact sheet on firefly-friendly lighting practices at