Are Fireflies Disappearing? What Environmental Factors are at Play?

Light. Dark.
Light. Dark.

Summer wouldn’t be the same without fireflies. But we might have to get used to it. Worldwide, the population of fireflies seems to be decreasing. Scientists are still investigating causes, but they believe that humans interfere with the habitats and mating rituals of the glowing insects.

The good news is, while researchers learn more about the problem, individuals can help in their own backyards.

Understanding the Basics

Helping fireflies begin with understanding them better. Let’s start with their name. Fireflies are actually beetles, not flies. They live in damp or wet habitats in temperate or tropical areas. Marshes, streams, forests, and lawns are feeding grounds for firefly larvae, providing plenty of tasty worms and slugs.

Though adult fireflies live one to three weeks, the entire lifecycle — complete metamorphosis — spans the seasons. During the summer, females lay eggs on or under the ground. To hide them from predators, eggs are often deposited beneath ground cover. After a few weeks, the eggs hatch and larvae, or glowworms, appear. They grow and eat and eat and grow until winter looms. Then, the larvae find a cozy spot underground or concealed by tree bark.

When spring rolls around, larvae leave their burrows to find food. After a few weeks of noshing, they pupate, creating hard outer shells. Inside, the insects are changing. In about two weeks, adult fireflies leave the pupas.

How did this Happen?

Humans are encroaching on firefly territories, and it seems to be affecting the insect population.

  • Habitat destruction: Fireflies like soggy, moist areas. When those are developed for human use, the insects are pushed out — and have nowhere to go. New houses, buildings, lawns, parking lots, streets, and highways take over the environment, leaving less space for the relatively long larval development stage.
  • Lawn chemicals: Outdoor chemicals might contribute to fireflies’ demise. Weed killers and pesticides may kill off organisms the insects eat. In addition, pesticides could be deadly to fireflies themselves.
  • Light pollution: Light pollution interferes with the very thing we love about fireflies: their flashing glow. They’re not the only creatures that exhibit bioluminescence, but they’re one of the most obvious. The light comes from a chemical reaction in an abdominal organ. Adults use specific patterns of flashes to signal potential mates.

Any artificial external illumination — building lights, streetlamps, and vehicle headlights— hinder this communication. If males and females can’t read each other’s cues because of these human intrusions, fireflies can’t mate. No mating, no future generations.

headlight, car headlight, car light

Making a Difference

You may not be able to singlehandedly stop the construction of a housing development that destroys habitat. However, you can take steps around your home to keep your own firefly community healthy.

  • Keep nature natural: Let logs and litter accumulate on your property. Firefly larvae live and feed in this environment. Plant a tree or two if your property is arboreally challenged. The best choice is a tree that’s fast-growing and native to your area. Pines are top of the list: their canopies give fireflies dark and secluded areas to flash away. The debris from these trees also creates stellar habitats for larvae’s prey.

While you’re allowing nature to thrive in your yard, let the grass grow, too — at least in some areas. While the neighbors might object to foot-high blades, fireflies often spend the daytime in tall grass. An artistically arranged spot of long grass in your yard will keep both your human and firefly neighbors happy.

grass, grassy, green

  • Welcome water: While you’re thinking about additions to your yard, remember that fireflies love moist, wet areas. Consider adding a small pond. Just don’t treat it with chemicals, because the tiny critters firefly larvae eat won’t survive.
  • Cut out chemicals: Since you’re not putting chemicals into your little pool, how about avoiding them completely? Chemical pesticides and weed killers can kill fireflies outright or, at the very least, make their surroundings uninhabitable. You want those larvae around, anyway: they eat garden pests.

The same goes for fertilizer. Firefly research is a developing field, but evidence suggests chemical fertilizers may hurt fireflies. Until there’s proof one way or the other, err on the side of caution. Use natural methods to feed your lawn.

  • Lose the light: Stop confusing fireflies with light. Don’t leave exterior lights on all night. Draw your curtains to keep indoor light from spilling out into the darkness.
  • Eschew earthworms: Some gardeners introduce worms to improve the soil, but most are not native to the northern U.S. Their job is to help natural debris decompose, but this reduces firefly larvae habitats.
  • Notify neighbors: Making some of these changes in your yard would be great for fireflies. Perhaps your neighbors would help, too — if they only knew what to do. Spread the word, and see if your local firefly population increases.

Did you know not all fireflies are bioluminescent? But even the non-flashy ones deserve a decent habitat. Though their environments are shrinking around the world, you can make a difference in your own little corner.

Megan Ray Nichols is the editor of Schooled By Science. She has a passion for green living and the environment. Follow her on Twitter @nicholsrmegan for more eco-conscious tips and tricks.

Megan Ray Nichols

Megan Ray Nichols enjoys writing about technology and various scientific topics. She is the editor of Schooled By Science. When she isn't writing, Megan loves to go hiking, fishing,and reading. On clear nights she likes to go star gazing in local parks.

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