In the spring of 1971, an entomologist scooped a small insect from a seemingly pristine creek in the Netherlands and pinned it in a museum drawer. The larva—a species of caddisfly—had stitched together a casing from scraps it found in its freshwater world. It was a normal act of insect ingenuity, nothing that would raise an eyebrow at the time.

But fifty years later, researchers took a closer look. Wedged among the usual grains and leaves were bright yellow fragments that didn’t belong. Under a microscope and the gaze of energy-dispersive X-ray spectroscopy, the truth snapped into focus: the insect had used plastic. Specifically, microplastic.

A builder of plastic

Caddisflies (Ironoquia dubia ) are builders. Their larvae construct portable cases from local debris. In the lab, they’ll use anything—gold flakes, pearls, even tiny rods of crystal. In the wild, they use whatever is available, including what humans left behind.

This solitary casing, built in a spring-fed stream in the Netherlands, is now the oldest known example of a wild freshwater animal using microplastic in its construction. It shifts the first documented case of this behavior from 2018 all the way back to 1971—an astonishing 47-year leap.

“Tellingly, 1971 is the first year in which microplastics were found in water samples from the North Sea containing “embarrassing proportions” of colourful synthetic fibers,” the authors of the new study write.

The team, led by Auke-Florian Hiemstra at the Naturalis Biodiversity Center in Leiden, didn’t set out to rewrite history. They were combing through museum specimens for overlooked signs of environmental change. What they found instead was the presence of synthetic polymers embedded in the life histories of aquatic insects.

“Microplastics have been impacting freshwater species for more than 50 years,” the authors write. “And continue to do so on an increasing scale.”

The 1971 caddisfly casing included artificial fragments, yellow and gray pieces of plastic. Chemical analysis revealed a cocktail of elements—titanium, barium, sulphur, zinc, and lead—consistent with plastic additives used in industrial production.

Right at the source

Importantly, this was no urban backwater. There was no clear sign of pollution at the time. The insect had been collected at the very spring that feeds the Loenense Beek, a rural creek supplying clean groundwater since medieval times.

This suggests that microplastics had already infiltrated even the most remote freshwater environments by the early 1970s. Not downstream or from sewage plants but at the literal source.

It’s a stunning reversal of assumptions. Scientists believed freshwater systems began accumulating plastic in recent decades. But this caddisfly—this one individual—shows how far back that story goes.

And it’s not alone. The researchers also discovered several caddisfly casings from 1986 that included blue synthetic fragments, likely from packaging foam. These larvae, collected near Oosterbeek, had also built their homes from a mix of natural and artificial materials.

Why this matters *a lot*

A single insect casing from 1971 might seem like a minor detail in the grand scheme of things. But it’s a smoking gun in the timeline of pollution—one that reveals how early and how deeply microplastics invaded ecosystems.

Microplastics are now among the most pervasive materials on Earth. They’ve been found in clouds, soil, sea ice, and rain. They’re in the deepest ocean trenches. They drift across mountain air. And they’re in us: we eat, drink, and breathe them.

Microplastic particles have been detected in human blood, breast milk, and even the brain. Recent studies estimate that people may ingest tens of thousands of plastic particles each year. One paper pegged the amount to the equivalent of a credit card every week.

So when a caddisfly larva unwittingly used plastic to build its protective casing in 1971, it wasn’t just an ecological oddity. It was an early warning sign of a global cascade. If plastic reached the base of freshwater food webs that long ago, it’s been filtering up ever since—from bugs to fish to us.

We were here and we were plastifying the world for over 50 years. We just didn’t notice.

The study has been published in the journal Science of The Total Environment.