5 min readYou may have happy childhood memories of running barefoot across the lawn to catch fireflies. But whether you call them fireflies, lightning bugs, or glow-worms, does it seem like you’re seeing fewer of them these days? And does this mean we may be the last generation to experience these tiny, shimmering jewels?
Fireflies (Lampyridae) have been around for more than 100 million years. There are more than 2,600 firefly species worldwide, with 178 species of firefly found in the U.S. But the truth about their future is concerning. “All firefly species, even those that are the least at risk, are facing significant threats,” says Richard Joyce, conservation biologist at the Xerces Society for Invertebrate Conservation. “There are about 18 species of firefly in the US that scientists have identified as being at a higher risk of disappearing.”
There are many threats to their existence. “They may not be extinct, but many species we associate with that spring and summertime magical glow are threatened by habitat loss,” says Eric Benson, PhD, professor emeritus and extension entomologist with Clemson University. “Once you change a landscape, say, with a bulldozer clearing land for a new development, you impact them. Some species have females that don’t have wings, so the males have to fly to find them. But once the females are wiped out, it’s nearly impossible to repopulate that area.”
In fact, many species only live in specific habitats such as wetlands, which are becoming increasingly fragmented. “For example, the Bethany Beach firefly only lives in small wetlands that are found on Mid-Atlantic Beaches, which have been greatly reduced by coastal development and are now threatened by sea level rise,” says Joyce. “The loopy five firefly, which gives an erratic, ‘loopy’ flash pattern of five pulses, is restricted to small, marshy wetlands in the Southeast. Many of these wetlands are outside of protected areas and are degraded or destroyed by increasing urbanization.”
Another threat is exposure to pesticides, which target all insects. “If you don’t want to see fireflies, keep a well-manicured lawn and use chemicals,” says Benson. In addition, artificial light also interferes with firefly reproduction because they can’t find each other with all those street lights and backyard light pollution illuminating the nighttime sky. And if they can’t see each other, they can’t mate and lay eggs to create the next generation!
Ahead, read on to learn more about these amazing insects and what you can do to help them thrive:
What Are Fireflies?
Fireflies actually are beetles, not flies. “Like ladybugs, they have two pairs of wings, and the front pair is hardened to protect the more delicate hind wings,” says Joyce. The most common firefly species vary by region, but there are a few species that are quite adaptable and widespread. “Most states have several dozen species of firefly, and a property with healthy firefly habitat can easily have half a dozen species or more.”
The big dipper firefly, also known as the common eastern firefly, is the most common backyard species in much of the country and is fairly adaptable to human-altered habitats. It’s even found in green spaces of metro areas around the country, says Joyce.
Their life cycle begins when adult females lay tiny eggs in damp, well-protected vegetation, such as in fallen leaves, in rotting logs, or in tall grasses. Eggs take a few weeks to hatch into larvae; in fact, fireflies spend most of their lifetimes as larvae—up to 2 years! The larvae eat snails, slugs, worms, and other soft-bodied invertebrates found in the leaf litter. Eventually, they grow and pupate to emerge as adult fireflies, which live for only a few weeks in spring or summer, says Benson.
How Do Fireflies Glow?
That magical glow is produced by a chemical reaction inside special cells in the light organs of fireflies, also known as their lanterns. “Oxygen and ATP, the energy molecule of life, react with two chemicals—luciferin and luciferase—and the result is light,” says Joyce. They use other chemicals, such as calcium and nitrous oxide, to regulate the supply of oxygen to turn their lanterns on and off.
As you may have guessed, fireflies glow for a specific reason, other than simply enchanting us. “Fireflies glow to send a message, both to each other and to potential predators. As larvae, fireflies use light to warn predators that they are toxic and taste bad,” says Joyce.
When it comes to finding a mate, fireflies use flash patterns to recognize members of the same species. “Males emit flashes or sets of flashes at predictable intervals, like a drummer setting the beat, and females will respond with a flash of their own when they see a flash that they especially like,” says Joyce. “The male will then approach the female, and a courtship conversation ensues in the form of blinks of light.”
How to Make Your Lawn Safer for Fireflies
If you’d like to help protect fireflies in your own little part of the world, there are several ways to do so:
Eliminate Pesticides
“Remember that fireflies are beetles, and many of the insecticides used for grubs, mosquitoes, and ticks are harmful to other insects, like fireflies, bees, and butterflies,” says Joyce.
Leave the Lawn Natural
If possible, leave an area of your yard more naturalized, with fallen leaves and bare soil. This provides shelter and an environment that’s rich in food for them, says Benson.
Keep Your Yard Dim
At the very least, turn lights off from dusk to dawn when fireflies are active. Or use a warm color of light, such as amber, and draw your curtains at night to keep your yard as dark as possible, says Joyce.
Shield Exterior Lights
This means that illumination from porch lights should stay on the porch, not spill into your garden or other habitats. Walkway lights should point downward, says Joyce. Or use motion detectors that light only when needed, or only turn lights on as required, such as when walking your dog.
Participate in the Firefly Atlas
You can learn to survey and count fireflies to help scientists learn more about what species are found, where they’ve disappeared from, and how their numbers are doing, says Joyce. Here’s how you can participate in this project to help scientists learn more about these fascinating insects.
