On my 77th birthday, in May of 2017, I opted to remain alone at my urban home to work a bit on my favorite hobby — a sizable streetside flower garden for butterflies and other pollinators. By dusk I had decided to retire early. First, however, I returned to my colorful garden to experience one last visual treat for my psyche.
Surprise! The fading light was punctuated by a dozen or so flashing pinpoints of light — yellowish white with a neon-like glow. As an entomologist, I knew that such pyrotechnics could be produced by only one thing: fireflies. But I hadn't observed these harmless and charismatic insects that herald summer on my premises for at least the previous four decades. Now, on this special evening, I felt as though I somehow had been transported back in time.
This resurgence of fireflies was personally poignant — and not just because of my birthday. You see, in 1973, when I built my first and only house in a new neighborhood that was being carved from a small patch of woodland on the outskirts of Baton Rouge, I tried to retain a natural look to the property. To do so, I landscaped my 1-acre tract as an urban wildlife garden based on the National Wildlife Federation's Certified Wildlife Habitat program. (My property is certified #4373.) Back then, fireflies were common. How well I remember walking outside on summer evenings for nature's post-dinner entertainment. The silent blinks always triggered an upwelling of serenity and relaxation. By the early 1980s, however, most of the vacant plots in my neighborhood had been developed, leaving my property the only vestige of nature. Alas, such was not sufficient to sustain a viable population of fireflies. My pre-bedtime elixir was no more.
And I wasn't alone. Turns out various news media were reporting that fireflies had disappeared from urban areas around the country. "Where have all the fireflies gone?" was a lamentation commonly addressed to nature journalists, and to me by my neighbors. But now the firefly pendulum has seemingly swung back. In response, I decided to gather some empirical data as a new research project.
Fireflies are the lightning bugs of our nostalgic childhood. Remember how on summer evenings we used to catch these blinking "fairies" to put into a jar so they could light up our bedrooms? In truth, fireflies are neither flies nor bugs, but rather beetles of the order Coleoptera in the family Lampyridae (the name refers to fire). No fewer than 200 species have been documented within the U.S., and there are about 2,000 documented species worldwide.
In Great Smoky Mountains National Park, a distinct species known as the synchronous firefly (Photinus carolinus) puts on a unique performance for a few weeks each spring at evening twilight. Thousands of the insects emerge in a forested cove to produce synchronous flickers reminiscent of a magical land of fairies. The National Park Service has even instituted a lottery system to control the number of visitors allowed to enter the park each evening to witness the display.
In the eastern United States, the most familiar variety is the common eastern firefly, also known as the big dipper firefly because of its characteristic "J" shaped flight while executing a double flash. I confirmed this species (Photinus pyralis) as the one in my landscape.
Fireflies, like other rank and file beetles, undergo a life cycle called "complete metamorphosis," which means that there are four distinct stages in development: egg, larva, pupa, and adult. Each stage requires specific living requirements. After mating, female fireflies lay as many as 500 eggs in low, shaded vegetation atop ground litter and loose soil, and in rotting logs. Upon hatching, the larvae are grub-like and are called "glow worms" because of their ability to produce cold light like that of their adults. The young hide in the darkness, capturing and sucking the body fluids from prey, such as snails, slugs, worms, other insects, and even each other. As such, firefly juveniles are important components of local food webs. The carnivorous youngsters grow slowly, taking one to two years to mature depending upon species and geography. At best, therefore, there can be only one generation per year. Next, the larvae transform into tough-skinned pupae that remain hidden in their dark venues until it's time for their final transformation into adults (in the Gulf South, it's midspring for P. pyralis). Understandably, manicured lawns, golf courses, recreational parks, and traditional residential neighborhoods don't make good habitat for fireflies. Making matters worse, fireflies and other insects on the wing at dusk are sensitive to the toxic sprays administered by mosquito abatement programs.
Fireflies are denizens of twilight. The insects shun light from both natural and artificial sources such as street lights and commercial floodlights — another reason for their urban disappearance. Strong light interferes with fireflies' own unique light displays. Called "cold light" or bioluminescence, their production of light is 100 percent efficient, meaning no heat is produced. The light is a result of a chemical reaction that takes place in the insect's abdomen. The reaction involves a special protein called luciferin (the fuel), a specific enzyme called luciferase (the spark), and atmospheric oxygen (the catalyst). Subtract any one of the ingredients and there is no light. Depending on species, light color ranges from yellow to white to green. (P. pyralis is a pale yellowish white.) The pattern for flashing or blinking is dependent upon species, too. In addition to producing a firefly's glow, experts note that luciferin has another important trait: a pronounced bitter taste. In theory, this confers to both larvae and adult fireflies' protection from predators. For a firefly, luciferin is truly part of the stuff of life.
I understand, of course, that a display of fireflies on my property in 2017 does not guarantee a similar event in the future. But it does confirm that my initial concept for a landscape that served as a haven for small wildlife has proven a success, and allowed me to observe fireflies on my own property. I've shared my observations (below) as well as some things to consider when creating your own firefly habitat and making your own observations.
Quite simply, when it comes to firefly habitat, location and time are very important. And because urbanized America just doesn't fit this bill, fireflies have gradually disappeared from many home turfs, except for mine and others like it. Designed with a wealth of trees, shrubs, and heavy ground cover — a vigorous vine called Asiatic jasmine (Trachelospernum asiaticum) — my de facto woodland is shaded but accented with a formal sun-drenched garden featuring seasonal flowers noted for attracting pollinators. My landscape is not only wildlife-friendly in general, but a textbook nursery for all life stages of fireflies. In return, my landscape provided me with a front-row seat to observe and document urban firefly behavior.
- I observed adult P. pyralis between May 23 and July 5, 2017, for a total of 44 days. The high point — the period when I logged as many as 15 to 20 individuals flashing during five seconds — was June 15 to 22.
- Fireflies were concentrated in the darkest and most heavily vegetated sections of my landscape and not in the open and more illuminated flower garden; the grassy strip between the sidewalk and street; or the street itself. The insects arose from heavy ground cover. This confirmed that trees and undisturbed, shaded soil are important to a firefly's life cycle.
- Flashings occurred relatively low to the ground (usually under 10 feet) with individuals demonstrating their double flashes while in a "J" flight pattern.
- Flight durations were brief. The longest was 70 minutes and the shortest was 16 minutes. Flights usually coincided with the onset of street lights and bat forays above my property. (Bats, however, didn't seem interested in the low-flying fireflies.) At this time the ambient light was adequate to distinguish the entire insect, not just its glow.
- Adults flew even when vegetation was wet due to an earlier rain shower.
- Flashings were sufficiently bright to be visible from unobstructed distances of at least 150 feet.
- I didn't observe individuals perched on vegetation, indicating that I was probably observing only males on the wing searching for females.
- I didn't observe adults feeding on flowers within my formal garden. Experts disagree as to the feeding habits of adult P. pyralis. Some investigators report that only females feed on nectar and pollen, whereas other authorities state that neither sex feeds at all. Unfortunately, I couldn't validate either hypothesis.
Attracting Fireflies to Your Property
To make your personal landscape firefly-friendly, you need to remember that adult fireflies don't fly far from their breeding grounds, and the insects require one full year in an undisturbed area to complete their complicated life cycle. Here are some tips for attracting fireflies to your property:
- If you're considering a new residence, select property that's close to a natural area that could be a reservoir for fireflies.
- Select a large area and plant deciduous (broadleaf) trees and bushes to create completely shaded ground.
- Install thick ground cover, such as an evergreen ivy or Asiatic jasmine, and don't disturb with human or animal traffic.
- Don't rake fallen leaves in autumn, but instead allow them to decay so they add humus to the soil.
- Don't use pesticides.
- Water during dry periods until the vegetation is well established.
- Install a flower garden close to the shaded venue with heirloom or native species to attract pollinators.
- Have patience! Years may pass before an adventuresome female firefly locates your landscape.
A retired professor of entomology and award-winning nature writer, Dr. Gary Noel Ross enjoys directing butterfly festivals for the North American Butterfly Association and exploring the swamps and marshes of his native Louisiana to research and photograph unusual aspects of nature.