The theory went like this: when confused by nighttime fog, fireflies can congregate into masses of hundreds, or sometimes even thousands. The fog reduces their ability to signal properly; the distance is shortened and the light becomes too diffuse. To survive and attract mates, individual fireflies started banding together. Once a small group is formed, they signal to one another with pheromones, and that triggers simultaneous illumination. It’s brighter, so even through the fog, solitary fireflies can find the group. So if you see a glowing beachball hovering over the lake on a foggy night, don’t freak out. It’s just fireflies trying to fuck.

I moved to the woodsy town in Vermont a couple years ago. During my first summer there, when the pea-soup fog rolled off the lake every evening, I saw those glowing orbs for the first time. That was before I’d learned they were fireflies, so I didn’t know what I was seeing. I watched from my porch as the ball floated across the yard at the edge of the forest. It was beautiful, but haunting.

The following morning, at the local diner, I brought up what I’d seen. The waitress laughed and said they were just the local fireflies. Apparently they’re considered a minor celebrity in the area. My buddy from college, Phil, was an entomologist. Bugs were his thing. So when I got home after breakfast, I called him up. I figured he’d be interested in the phenomenon.

Apparently, “interested” was an understatement. I guess fireflies had never been observed doing something like that anywhere else in the world. I told him he’d be welcome if he wanted to make the drive up from Connecticut and stay for a few days to see them for himself. He did.

The next day, Phil arrived at dusk. Great timing. I gave him a quick tour of the place, then we brought a six pack out to the porch and waited for the fog to move in.

In a steady, slow creep, the fog poured across the lake, into the forest, and swallowed my yard. The moonlight was a dull haze above our heads, and right away we saw individual fireflies trying to locate one another with their bioluminescent shouts.

We waited and drank beer after beer as we caught up on the goings on in our respective lives over the last ten years. After a couple hours, I caught a glimpse of something glowing on the other side of the trees, right by the lake. I pointed and Phil stood up and went to the edge of the porch.

“Wow,” he breathed, and I could sense his genuine excitement. It was contagious. I got up and stood with him as we gazed at the orb of softly undulating light, our beers forgotten.

The mass of fireflies approached the edge of the yard, every one of its members flying in a tight, spherical pattern. “I don’t believe my eyes,” Phil said. “That behavior’s never been documented in that species.”

The sphere’s light waxed and waned, and solitary fireflies all over the yard, disoriented in the morass of fog, began to move toward the group. They incorporated themselves into the luminous mass.

The group turned back toward the forest and eventually went out of sight.

“Pretty cool, right?,” I asked.

“One of the coolest things I’ve seen in my career,” he agreed. “I’m going to write up a report tomorrow morning, then tomorrow night I’m going to see if I can record it with my phone. Might not come out too great in the low light, though.”

“Worth a shot,” I said. He nodded.

The next morning, I made coffee while Phil typed up his report. I could tell he was impatiently waiting for the evening, so I made a list of local stuff we could do to help the time pass more quickly for him. He finished up and we went out and had a fun, eventful day.

The sun drowned itself in the lake while we ate dinner. Individual fireflies right outside the window were already signalling, as if they wanted to do as much talking as possible before the fog made their job harder. I told Phil to go outside and leave the dishes to me. He didn’t argue.

I watched from the kitchen window as Phil dragged a lawn chair out to the line where the yard met the forest. He sat with his phone and his tablet and waited while fog drifted in around him.

He didn’t need to wait long.

An orb of fireflies coalesced no more than 20 feet from my friend. I stopped washing up and stepped out onto the porch to watch Phil get his footage. He held his phone out like he was Spielberg filming his next award-winning movie.

“I don’t know if this is gonna work,” he called to me. “Too damn dark.” He put the phone on the chair and tried to record with the camera in his tablet. “That’s a little better,” he said. “I think the camera in this thing is better in low light.”

He recorded for a minute, then I saw two more orbs coming in off the lake. Perfect. The waitress told me the smaller masses would sometimes join bigger ones, so I hoped that was the case. Phil noticed them too and called out, “that’s so cool!”

The new masses of fireflies converged on the one in the yard. The fog was dense and I was having trouble seeing Phil, but the glow of the bugs had produced a peaceful, pale-yellow haze.

I heard Phil swearing to himself. The filming wasn’t going very well.

“How about a picture?,” I asked. “That might help with the light problem. Try to take a lot of shots in a row and maybe you can animate them in the computer afterward.”

Phil didn’t say anything, but I saw him move the tablet down as if he were changing some settings. He held it back up, and flashes exploded through the fog as he took picture after picture.

“This is gonna screw up the way their illumination looks,” he shouted, “but at least I can show how they’re clustered together.”

Flash after flash after flash bloomed through the thick fog. Above us, the sky lit up as distant lightning announced a coming storm. Indeed, a storm had been forecasted for the early morning hours, but apparently it was ahead of schedule. “You see that?”

“Yeah,” Phil replied. “I’ll get inside before the rain.”

He kept snapping pictures. On the outskirts of the yard, I noticed more light. There were new orbs. Lots of them, ranging from ones the size of a lemon to others the size of watermelon. “Phil!,” I shouted, “check those out!”

More orbs coalesced and moved in the direction of Phil, apparently attracted by the strobing camera. The lightning flashed again. Brighter this time. Closer. There was no accompanying thunder.

Now there were tens of the firefly clusters, and the yard was a blur of pale yellow that threatened to compete with the camera flashes. “This is fucking awesome!,” Phil hollered, and almost as if in response, more lightning lit up the fog. It was almost blinding now, and I said to Phil we should probably go in. “Hang on,” he replied. “I’m almost done.”

All the firefly masses formed one colossal ball the size of mid-sized car, which hovered directly above Phil. There was another burst of lightning, this time accompanied by a gust of wind so powerful it knocked me down. The mass of fireflies scattered. And Phil screamed.

I jumped back to my feet just in time to be nearly blinded by an explosion of intense light coming from where my buddy was standing. I squinted and tried to acclimate my vision. Phil kept hollering. “What’s going on?!,” I shouted to him. There was no reply other than hysterical gibberish.

My eyes slowly acclimated to the light and I when I realized why Phil was screaming, I gasped and backed up to the house. A glowing firefly the size of a school bus was pinning him to the ground. He struggled and thrashed, but the insect must have weighed tons. Its wings fluttered and a hurricane-force wind pushed me against the house and flung leaves and branches from the nearby trees.

“Help!,” Phil shouted, over and over. I was too terrified to move. I could only watch as the hideously luminescent creature held my friend under its bulk.

A small drop of pure, white light fell from the mandible of the monstrous bug. Phil’s scream grew high pitched and inhuman. More of the liquid light drooled from the firefly’s mouth. I smelled burning. Burning clothes. Burning grass. Burning meat. A pool of radiance formed where Phil was pinned. His screaming stopped.

The firefly lurched up and took to the air, the wind from its wings shattering windows in the house and tossing me to the ground. It was gone. The light was gone. The orbs were gone. All that remained was a puddle of horrible luminescence.

I ran in the house and dialed 911, spoke to them for a minute, then stepped warily toward the liquid light. The stench was overwhelming. I gagged and got closer. The fog was making it difficult to see anything with proper resolution. But soon, I was only a couple feet away. It all came into focus.

The acidic light, which was now starting to dim, had destroyed everything it had touched. Tattered, singed clothing still smoked. The skeletal remains of my friend still steamed. And gripped in his bony hand, the melting tablet still sat, its flash strobing with dying pulses as the acid ate it away.

Unsettling Stories is on Facebook.