“Will you come into my parlour, said the spider to the fly? I have all kinds of curious things to show you when you’re there.” Generations of parents have recited English author Mary Howitt’s 1829 poem to warn children away from this kind of temptation.

The need for warning hasn’t changed. Two centuries on, unsuspecting flies, mosquitos or even bees still succumb to the spider’s lure and end up woven into intricate webs hanging from the top corner of seldom-cleaned PMMA bus stop shelters. It’s the “curious things” within that have changed.

Beyond animal matter or silvery slivers from a discarded chewing gum wrapper, modern-day spider webs contain microplastics. Invisible in the air we breathe, the jewel-like particles that resemble sparkling dew may be bits of PET or PVC.

“The sticky webs are an ideal trap,” says Barbara Scholz-Böttcher, who oversaw the team at Germany’s Oldenburg University that examined the webs. The PET may come from the clothes you’re wearing, the PVC particles from the tyres of passing cars – or buses. In the web samples, microplastics accounted for 10% of the volume on average.

The university plans to conduct more field studies, but next time you hear it thunder, hide in a bus stop shelter: part of your belongings may become part of the next project.