The Secret Lives of Fireflies

As I sit here typing, I’m still bundled in flannel pajama pants and thick merino wool socks. The thermometer reads just above freezing, and the wind outside cuts through my light sweater with ease. It’s still winter, but there are signs of spring. The Baltimore Orioles visiting my jelly feeder are becoming brighter by the day as they molt into their spring plumage. But my mind wanders to the summer ahead, one full of friends visiting, cooking outside, and music around a fire pit.

Until now I haven’t thought much about where fireflies come from, just that they are. To me, and I assume to many, they’re synonymous with summer. In a good year, a summer evening can see a spectacular emergence of fireflies rising from the grass and woods edge, filling the yard with blinking lights, their conversations left untranslated to us, but nevertheless emotive and captivating.

Fireflies are beetles, and as beetles they go through four distinct stages in their lifecycle. While we’re most familiar with them as bioluminescent adults, most of their lives are spent as voracious predatory larvae, up to two years feasting on slugs, snails, and mosquitoes, before pupating underground and emerging as adults after only three weeks. In fact, the egg, pupae, and adult stages together comprise roughly nine weeks of the firefly’s life. It’s no wonder their conservation is so heavily dependent on the health of our soil, leaf litter, streams, and marshes, where they live out their months as larvae.

Therefore, the adults we see in the summer are the products of the adults from one and two years prior. Adults who were courting each other with their distinctive blinking patterns; patterns that encode their species and their intent. Patterns that say, in the parlance of Flight of the Concords: “Ohhh yeeeah. You know what time it is? It’s business time.”

What fascinates me is that for something so seemingly common, scientists still have much to learn about. New Jersey is home to at least 30 of the 150-ish species documented in the United States, the uncertainty of these numbers suggesting there are still new species to be found.

You may have heard about, or even witnessed, the reduction of fireflies in your area. Conservation groups like the Xerces Society have sounded the alarm about the loss of these species worldwide. Habitat loss and degradation are the main drivers, and since you now know about their lifecycle, it becomes clearer how the one- to two-year larval stage can be particularly vulnerable. Pesticide use in and around wet meadows and stream corridors, removal of leaf litter and fallen dead wood, light pollution, and severe droughts due to climate change, all likely play a part in their decline.

So, what can we do? Organizations like the Xerces Society and Firefly.org provide tips for making a difference.

You can even certify your property as “firefly friendly” by:

• Providing undisturbed cover for adults and growing larvae
• Encouraging plant diversity to preserve soil moisture
• Reducing light pollution
• Restricting pesticide usage

In our own yard, we’ve made several changes. We put our address on the no-spray list for the mosquito commission, which means being vigilant about standing water on our property. We now mow our lawn three notches higher, maintaining more moisture and structure in the soil while also allowing more flowers for native pollinators. We keep the back of our property wilder, with undisturbed leaf litter that benefits many insect species including overwintering moths and butterfly larvae. We’ve replaced bright outdoor lights with ground-level solar LED walkway ones, so we can see at night without flooding the yard with unnecessary light pollution.

Our individual efforts alone won’t bring back fireflies to our neighborhood, but working together with neighbors to create wildlife-friendly yards can have an impact. We’ve seen it work for the Monarch Butterfly in Cape May, so why not for the many species of firefly that grace our region? As I sit here now, with an eye on the thermometer, I know that somewhere in our yard, underground, those larvae are weeks away from stirring, preparing for the next leg of their journey. Just thinking about that raises the temperature in my house a degree or two, and I can’t help but smile. 

I don’t know about you, but as much as I’m looking forward to outdoor dinners and music around the campfire, I’m eager to welcome this year’s fireflies to my yard. I can’t imagine summer without them, and if we work together, I hope we never will.