Summer evenings were once full of fireflies, but in many places those times are now a distant memory. Yes, these beautiful beetles are dwindling in number – but what has caused their disappearance?

Image: MARIO VAZQUEZ DE LA TORRE/AFP/Getty Images / S. Rae

Many of us remember how the summer evenings of our childhoods used to begin – with the dazzling displays of fireflies. We used to watch the countless glowing orbs trailing their colors through our yards and across the darkening sky. But these days, the creatures’ light has dimmed in a lot of places, leaving gardens standing dark and empty.

The term firefly has become synonymous with Joss Whedon’s noughties sci-fi TV series of the same name. But the show of course owes its title to an order of beetle – otherwise known as Lampyridae. And because of their most distinguishing feature, the creatures in this family of insects are also known as lightning bugs.

But what’s the source of the beautiful light shows? Well, most fireflies have glowing abdomens, and it’s these that make them highly visible in the darkness. The incredible displays are actually examples of bioluminescence – or organically made light – created by chemical reactions. And they also serve an important purpose for the beetles’ lifestyles.

When twilight falls, male fireflies use their glowing bodies to signal for potential mates in a variety of ways. The sender’s emissions of light reveal much about himself to the female, which appraises the potential suitor’s qualities. And if she deems the pairing suitable, the female then responds to the courtship with her own lights.

The resulting breeding creates firefly larvae – sometimes called glow-worms – which emit their own bioluminescence. And the beetles prefer moist and tepid climates, so they’re most commonly found in damp woodland or marshes. In fact, even after maturing, the glow-worms don’t stray far from their birthing grounds.

As for their eating habits, although some adult Lampyridae subsist on nectar and pollen, others are hunters – as are the majority of the larvae. These hungry juveniles actively prey on worms, snails and insects. At the same time, fireflies themselves have few predators precisely due to their phosphorescence – a quality that you might well think would attract unwanted attention.

But here’s the thing: the chemicals produced in the beetle’s bodies are foul-tasting – if not outright poisonous. Indeed, it was once thought that fireflies’ red, yellow or green abdomen lights serve as warnings of potential threat. And yet despite this, there are nevertheless hungry creatures out there that are unfazed by the firefly’s decidedly unappetizing taste.

For example, Photuris – or the femme fatale firefly – is a predatory Lampyridae that hunts its own kind. These cunning killers answer male courtship signals, convincing the unwary suitors that they have each found a mate. The femme fatale then devours the love-struck beetle when he comes calling for his would-be partner.

All the same, fireflies hold an arguably rare place in people’s perceptions as welcome beetles, and many folk look forward to their presence. After all, not only are they fantastical-seeming creatures, but they also mark the arrival of summer. Their hibernation period ends in spring, and as the seasonal climate changes, the fireflies appear.

Or at least, this mass appearance used to be the case. You see, firefly numbers have fallen dramatically in recent years, meaning people are seeing fewer and fewer of them. Some sources, such as Firefly.org, even speculate that the creatures might become extinct in our children’s lifetimes.

Firefly.org reports, “There are signs that our kids may not grow up with the same firefly memories that we had. That’s because fireflies are disappearing from marshes, fields and forests all over the country – and all over the world. And if it continues, fireflies may fade forever, leaving our summer nights a little darker and less magical.”

Now the reason for the fireflies’ disappearance isn’t entirely clear, but it’s likely the result of a number of contributing issues. Yes, experts have identified various problems that could be causing the decline. And the first is a threat faced by many species: loss of suitable habitat.

As previously suggested, fireflies don’t have wide-ranging habitats and usually remain in their birthplaces. So when urbanization spreads, housing and roads claim the insects’ environments. The fireflies thus have nowhere to go or breed, and this leads to the end of individual colonies.

Furthermore, it’s not just the lack of nesting places that’s the problem; it may also be the general noise and increasing population of humans. According to Firefly.org, areas that once flourished with fireflies have since suffered a decline in the insects’ numbers because of the presence of people.

The second major factor that researchers claim is having an impact on fireflies is artificial light. For a creature that relies on its own bioluminescent radiance to communicate, man-made light is a big problem. Car lights, street lights and house lights all confuse fireflies and impact on their courtship.

Firefly.org also reports that pesticides, too, might be problematic in the Lampyridae’s environment. These poisons last longer in damp environments, which the beetles favor. And pest control chemicals could be responsible for killing local insects, thus reducing the firefly’s food source.

Now if you want to do your part to keep firefly species alive, a good place to start is in your own backyard. Naturally, making the garden beetle-friendly involves making sure you keep any moist landscape features intact. And, given the threat outlined above, avoid pesticides as much as you can, too, as they can kill both fireflies and their prey.

What else? Well, just in case your yard is attracting the kind of fireflies that flourish on nectar, ensure you plant plenty of flowers. This is especially something to consider given the fact that in addition to helping Lampyridae, the practice will also draw in other species of concern such as bees. Oh, and don’t forget to throw in some bushes to provide daytime hiding places for the night-loving fireflies.

Lastly, try to keep your lights on low, and avoid unnatural light features in the designated firefly section of your yard. Bear in mind, too, that you won’t be alone in your efforts to save fireflies, as there are other people working to keep the creatures alive as well. And one great example of such human intervention is in the Smoky Mountain National Forest in Tennessee.

The forest is home to many thousands of fireflies that take to the air every summer. It’s an incredible sight – and one that draws millions of visitors each year. “This breathtaking show put on by nature resembles a psychedelic combination of stars falling and fireworks exploding,” the park states on its website. “It is an immersive experience that you will never forget.”