Few things in nature inspire wonder and awe like organisms that glow in the dark. A chemical reaction in living things can cause them to make their own light. This is called bioluminescence. Many species have evolved to radiate light throughout history. It can occur in bacteria, fungi, insects, birds, and even marine life. Some living things emit light in short bursts. Some emit a steady glow. The Southern US is home to many of nature’s night lights. We’ll tell you when and where you can find things that naturally glow in the dark. Nighttime is the right time to discover bioluminescence in your backyard. This is the first in a two-part series.
What’s the purpose of bioluminescence?
Some creatures use light to attract prey or a mate. Light can also be a defense to ward off predators. Some use light to mimic other species or as camouflage. Sometimes it’s used to communicate with the same species. Some even use light to illuminate their surroundings. We don’t know what the function of bioluminescence is for every species. We still have a lot to learn about why some organisms glow in the dark. But we do know a lot about bioluminescent beetles like fireflies!
Fireflies and lightning bugs
The scientific name Lampyridae is Latin for “shining light”. There are around 2,000 species of Lampyridae across the world. In North America, there are more than 125 known species. There’s no difference between a lightning bug and a firefly. You can use the terms interchangeably. What you call them depends mostly on where you grew up. But Lampyridae are neither flies nor bugs; they’re beetles. Beetles are unique because they have hard wing covers and chewing mouth parts. No matter what you call them, they’re a magical sight to behold!
Fireflies have a 4-stage life cycle. They spend most of their life (1-3 years) underground. They lay eggs in moist soil. The eggs take around 3 weeks to hatch. They’ll spend 1-2 years as larva before transforming to pupa for another 3 weeks. Finally, they emerge from the ground as adults and live for 3-4 weeks. In general, adults emerge during late spring and midsummer. They’re most active between late May through early August. Once they reach adulthood, their goal is to mate and spawn the next generation.
Lightning bugs vary in color, shape, and size. But many appear very similarly. Fireflies produce light in their larval stage, and many also emit light as adults. Some glow and some flash. The frequency and pattern of a male’s flash and a female’s response is unique to each species. It’s their love language that identifies each other in the darkness. These mostly nocturnal beetles thrive in temperate and tropical climates. They flourish in moist regions and prefer marshy, wet, wooded areas. Let’s talk about some of the most well-known lightning bugs you can find in the Southern US.
What do you call this bioluminescent beetle?
Synchronous Fireflies
There are two types of synchronous fireflies in the Southeastern US. This species flashes in unison with one another in a delightful display. Their scientific names are Photinus carolinus and Photuris frontalis.
Smokies synchronous firefly
Photinus carolinus are commonly known as the “Smokies synchronous firefly.” Adults are about ½ an inch long. They’re mostly black with yellow-lined wing covers. Their see-through head shield has a reddish splotch and a dark rectangle at the center. They have long, dark antennas. They emit a yellow-green flash from the pale segments of their lower abdomen. Males light up in a flash train. Their pattern is 6 flashes about half a second apart, followed by a pause of 6 seconds. Then they repeat the pattern as often as every 9 seconds. They do this while flying fairly low (3-7 feet) off the forest floor. Their display can appear like a rippling wave of light. By the end of the night, their light can appear less bright and more orange.
When and where you can find Smokies synchronous fireflies
Peak Smokies synchronous firefly activity varies from year to year. It depends on weather, temperature, and soil conditions. It can range between late May to late June. Their light show begins about 30 minutes after sunset and can go on well after midnight. Undisturbed, dark forests are their prime habitat. You can find the Smokies synchronous firefly beyond the Great Smoky Mountains. Look in northern Georgia, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia. They prefer mature hardwood forests (65 years or older) in mountain river valleys above 1,400 feet. They avoid thick underbrush and favor small clearings surrounded by open forest.
Snappy single synch
Photuris frontalis are commonly known as “snappy single synch.” Adults are ½ – ⅔ of an inch long. Males are larger than females. Adults are more rounded looking than other lightning bugs. They’re mostly black with pale yellow, almost translucent lined wing covers. Their head shield is translucent with a dark rectangle or hourglass at the center. They have long thin antennas. Males have two light producing segments on their lower abdomen. Females have a unique split lantern on the top of their two light segments. Snappy single synchs get their name from their quick and constant flash. They emit light two times per second in prolonged bursts. Up close they emit a deep yellow flash, but the light can appear white from afar. Males fly low (2-5 feet) above the ground searching for females in the leaf litter.
When and where you can find snappy single synchs
Peak snappy single synchs activity usually begins in mid-May to early June. The window to observe snappy synchs lasts just 2-3 weeks. Their light displays begin about 40 minutes after sunset and can last for 1-2 hours. They’re found in Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, and Tennessee. This species prefers the edges of mature cypress swamps and forested bottomlands. They need moist wooded areas with water sources nearby.
Park lotteries for synchronous fireflies
People will travel from all over the world for the chance to see synchronous lightning bugs. You can watch Photinus carolinus at Great Smoky Mountains National Park and at Grandfather Mountain in NC. You can watch Photinus frontalis at Congaree National Park in SC. These parks hold an annual lottery to keep visitation manageable during peak times. But there are other locations where you can find synchronous fireflies if you look.
Blue ghost fireflies
Phausis reticulata are better known as blue ghost fireflies. They’re a rare and elusive species. Adult males are tiny at ¼ – ½ of an inch. Their bodies are dark brown to black. Their rounded head shield is black and includes a windscreen around their large eyes. It looks eerily like Darth Vader’s helmet. They have a short and a long set of antennae. Males have two light-emitting segments on their lower abdomen. Females stay larvae throughout adulthood and are known as Appalachian glow-worms. They have no wings and can’t fly. They’re usually even smaller than the males at ⅛ – ⅜ of an inch. They look like a small golden grain of rice. They crawl along leaf litter on the ground, waiting for a mate.
Instead of flashing, male blue ghosts emit a steady glow that can last up to a minute or more. They fly very low, 1-4 feet off the forest floor. It can sometimes look like they’re shining a spooky spotlight. Seeing them in nature can give an enchanted forest feeling. At a distance, blue ghost males emit a bluish-white light. But the color can appear more green the closer you get. This is due to the way the human eye functions. Light sensitivity can alter the color we perceive. Females give off a faint green glow from 4-9 spots on their bodies.
When and where you can find blue ghost fireflies
The window to observe blue ghosts is just 2-4 weeks every year. They can have two peak periods. The first lasts from mid-April to mid-May. Then they can reappear in mid-June. Blue ghost light displays begin about 30 minutes after sunset and last up to 90 minutes each night. They prefer warm temperatures and moist to wet, undisturbed wooded areas. But you can also find them in dry woods and dry high ridges. The most common place to see them is in the Southern Appalachians of North Carolina. But they’ve been reported in Alabama, the Georgia Piedmont, South Carolina, and Tennessee. You can also find them in some isolated pockets of Northern Florida.
Sadly, blue ghost populations are dwindling from habitat loss and light pollution. Logging and development contribute to their decline. Any activity that disturbs the forest floor can destroy their habitat. Humans are their biggest threat. Be careful not to love these tiny bioluminescent beetles to death. If you’re going out at night to see blue ghosts, take precautions. Check out our visiting firefly habitat etiquette below.
Common eastern firefly
The common eastern firefly goes by several names. It’s the lightning bug that most people east of the Rocky Mountains will find in their backyards. Its scientific name is Photinus pyralis. They’re also called “big dipper” or “J-stroke” fireflies. This is because of their unique flight and flash pattern. They measure ⅓ to ¾ of an inch long. Adults are mostly black with yellow-lined wing covers. Their head shield is a pale yellow with a red splotch and black dot in the center. Males usually have much larger eyes than females. They both have dark, segmented antennas. Males have two light-producing segments on their lower abdomen. Females have a heart-shaped lantern on a single segment of their abdomen. Females often have two dark triangle markings on each side of the lantern. This has also earned them the name “tornado tail.” Both sexes emit a yellow-green light that can look like shooting stars in the night.
Male big dippers fly in a vertical orientation in a U-shaped dipping pattern. They form a distinct J-shaped courtship flash that lasts for a little more than half a second. Males will flash every 5-7 seconds. They fly low (2-3 feet) above the ground early in the evening. Then they’ll fly very high later in the night. Many end their displays in the treetops. Females remain low to the ground on leaves or grasses. They twist their abdomen towards the male and emit a single flash to alert their interest. Males will present females with gifts to sway their mating selection.
Fascinating facts about big dipper fireflies
Male big dippers can fall victim to looking for love in all the wrong places. Photuris versicolor fireflies, also known as femme fatales, will mimic female big dippers. They will attract, kill, and eat male big dippers. Big dippers have a defensive chemical called lucibufagins. Photuris versicolor lightning bugs don’t. When Photuris females eat male big dipper fireflies, they absorb the chemical. This helps them deter predators like spiders and birds, increasing their chances of survival. Luckily, male big dippers have another defense mechanism. They can secrete a gooey substance. It locks the jaws of female Photuris versicolor long enough that the big dipper can escape.
When and where you can find big dipper lightning bugs
The best time of year to find big dipper fireflies is in the late spring and summer months. But you can spot them as early as May and as late as October, depending on the area. Peak activity begins near dusk or about 20 minutes before sunset. Their displays can last for several hours. I’ve seen them flashing well past midnight. Their range is vast. It expands well beyond the Southeastern states. You can find them from Texas to Ontario. They need areas with high moisture to survive. You’ll find big dipper lightning bugs in many habitats. Tall grassy meadows, open fields, wetlands, desert valleys, and dense woods and forests. I see these in my own backyard every spring/summer, and it never fails to inspire me with a deep sense of awe and amazement. It’s something I look forward to every year.
Glowing click beetles
I grew up in South Florida, and I always mistook glowing click beetles as a kind of lightning bug. My family called them cocuyos. These bioluminescent beetles are similar, but they’re in the Elateridae family. Adult glowing click beetles are dark brown to black and range from 1 – 1 ¾ inches in size. They have long, dark antennae and small eyes. Their wing covers have a ridged pattern running lengthwise on their body. It gives them the appearance of armor.
Adult glowing click beetles have two bioluminescent organs on their head shield. The lanterns emit a steady green, glowing light and look like “false eyes.” They don’t flash, but they can vary the light intensity they emit. This bright to dim glow can give the appearance of flashing. Some believe that glowing click beetles use this light to scare off predators. Their larvae are also bioluminescent.
When and where you can find glowing click beetles
You can find various species of glowing click beetles in coastal regions of the Southern US. Especially in Florida, Georgia, and Texas. They prefer sandy and forested areas. I remember seeing them in the later summer months. Typically from August through September.
Firefly etiquette when visiting their habitat
- Stay on designated trails or viewing areas. Trampling off-trail can damage or disturb lightning bug habitat. Worse, you could step on female fireflies that stick close to the ground.
- Get settled early. Lightning bug displays usually begin shortly after sunset. Have yourself situated comfortably well before the sun goes down. Plan to bring a comfortable chair, blanket, or anything else you may need to stay put for some time.
- Keep it dark. Car headlights, lamps, flash photography, and flashlights disturb fireflies. So can the light from your phone or tablet. Do not introduce light pollution to lightning bug habitat. If you must use a light, use special red light bulbs or filters. Point your red light directly at the ground. This will reduce disruption to lightning bugs and other visitors.
- Avoid insect repellent. Wear long sleeves and pants to avoid biting insects instead. If you must use insect repellent, apply it well before you arrive. Do not spray insect repellent at the firefly viewing site. It will repel fireflies.
- Be respectful of other visitors and wildlife.
- Observe quietly. Remember you’re in nature.
- Watch, don’t catch. Adult fireflies have limited time to live. Catching them can result in unintentional harm to future generations.
- Leave nothing behind, take only memories. Make sure to remove any items or trash you bring in with you. Take non-flash photos and make some lifelong memories you’ll never forget.
Are fireflies and lightning bugs endangered?
Fireflies are a source of child-like delight. People of all ages can find inspiration and a deep sense of awe watching them. That alone makes them worthy of studying and protecting. But lightning bugs are also an important indicator species. When they’re abundant in an area, that’s a good sign that pollution is low and the environment is healthy. When their populations decrease or disappear, that’s a bad sign. It means that the environment is suffering.
The conservation status for most fireflies in the US hasn’t been evaluated. There’s little funding to study them. But a 2024 study compiled from citizen scientist data raises alarms. It shows that North American firefly populations are in decline. Lightning bugs need wet, dark, undisturbed forests to survive. These habitats are becoming more scarce in the US.
Human activity poses the greatest threat to fireflies. Climate change increases droughts and surface temperatures. Hotter, drier habitats are unsuitable for their survival. Air and water pollution have a devastating impact on their populations. Deforestation and development destroy their habitats. Light pollution disrupts their mating and development cycles. Pesticides can kill lightning bugs at all stages of their life cycle. Humans will harvest fireflies for scientific, medical, and chemical purposes. But new synthetic options make this practice cruel and obsolete. Unfortunately, in some rural areas harvesting continues. A conservative estimate is that 10% of all firefly species are in danger of extinction.
How can I protect fireflies and lightning bugs?
Commit to doing everything you can to ensure fireflies and lightning bugs thrive. To brighten the lives of future generations.
Sign the pledge to protect lightning bugs!
Certify your property. Firefly Research & Conservation offers a firefly habitat certification program. Commit to making your backyard or land a permanent place for lightning bugs to thrive. You’ll even get a beautiful sign to post.
Want to do more?
Experiences that inspire wonder can help reduce depression and improve mental health. Southern forests and wetlands are filled with awe-inspiring phenomena. That’s one of many reasons we must do everything we can to protect them. Appreciating the beauty around you, can help you find your own glow within. There are few things as marvelous as those that light up the night. I hope this inspires you to explore the many living things that glow in the dark. Be amazed by the bioluminescence you can find in your backyard.
The best way to protect bioluminescent species is to protect the places they rely on to survive.
Act now to protect wildlife and wilderness.
Learn more about bioluminescent beetles of the Southeast in Fireflies, Glow-worms, and Lightning Bugs by Lynn Frierson Faust.
Check out the nonprofit Firefly Conservation & Research at firefly.org.
Explore the other blogs in our Biodiversity in Your Backyard series.