A creeping mass of insect larvae near a Denali lodge raises the question: ‘Am I hallucinating?’

Elaina O’Brien ran back to staff housing on a busy morning at the Camp Denali lodge last Friday to grab the radio she’d forgotten at her cabin.

She looked down at the flagstone path, and what she saw made her think: “Am I hallucinating? Did I have some kind of psychedelic mushroom for breakfast? What. Is. That?”

Was it a slug? A desiccated animal body?

“But it was right on the staff trail!” she said. “And I looked and I was like, ‘Oh my God, am I seeing this for real? Like, it’s just a million bugs, being herded by these other bugs, in this slimy trail.”

O’Brien is the housekeeping and serving coordinator at the lodge, which is in the Kantishna area at Mile 89 of the road that cuts through Denali National Park and Preserve.

It turned out she was looking at a new, yet-to-be-named species of a type of fly called a gnat snakeworm. In that moment, they were traveling together as larvae in a “rare phenomenon,” said Derek Sikes, curator of insects and professor of entomology at the University of Alaska Museum of the North and the University of Alaska Fairbanks.

[Video above: Watch the mass of gnat snakeworm larvae move near Camp Denali on July 8. (Courtesy Jenna Hamm)]

Hundreds of larvae, each almost a centimeter long, form the crawling column. Columns of larvae can stretch up to 2 or 3 feet, and they may gather in that formation only for a few hours, Sikes said.

Sikes has been studying these Alaska insects since a docent at the Museum of the North brought in a picture of the larvae and some specimens back in 2007.

“It was completely ‘X Files’ to me — I had never heard of or seen this phenomenon before,” he said.

And he wasn’t the only one. Despite how conspicuous the formation looked, longtime naturalists hadn’t seen it in the state either, Sikes said.

Since then, gnat snakeworms in this column-like formation have been reported near Fairbanks, in Katmai National Park and Preserve and in Kenai Fjords National Park. But the Denali National Park-area sighting was a first, Sikes said.

He then raised some of the larvae into adult flies, which allowed him to figure out what type of flies they were. By looking at their DNA and studying their anatomy years later, Sikes determined these gnat snakeworms were a new species, distinct from their closest relatives in Europe — which are also known to move in a similar mass procession.

“Some people find it sort of visually repulsive because it does look a little strange, but it’s not harmful to people,” Sikes said. “These things are not a problem for anybody. They’re not invasive. There’s nothing to worry about with them.”

It’s not yet known why there weren’t observations of these snakelike formations in Alaska before 2007, Sikes said. It’s likely someone would have reported it, but there’s no evidence of that, he said.

But even why the insects do it is a mystery.

“Nobody really knows exactly why they migrate in these great numbers together and also why they take this particular shape of a long column,” Sikes said.

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There are a couple ideas about why they travel like that, Sikes said. It may be that since the larvae tend to live in moist, dark and cool areas, they try to stay closer together on a road or trail that’s exposed to sunlight so they lose less moisture.

Or, Sikes said, they might be traveling that way because it makes them look like a larger animal.

“It’s just a fascinating piece of nature that most people have never experienced or seen before,” Sikes said. “Even for most entomologists, it’s a really rare phenomenon.”

Sikes and colleagues plan later this year to publish their research on the insect and name the new species.

At the lodge on Friday, O’Brien said she “got way down close” to look at the gnat snakeworms and realized other people needed to see. She ran to the staff room and urged the guides to come and take a look. The group watched as the insects edged off the path.

And then, after it had materialized, the line of larvae soon disappeared without a trace.

“When we went to go back a couple hours later, there wasn’t even, like, a slimy slug trail or any, like, bits and pieces left behind,” O’Brien said.