NGM Blog Central - In Rotterdam, Webs of Mystery - National Geographic Magazine

Bushes, trees, an entire car shrouded in a ghostly white web—the sights last spring in the Dutch city of Rotterdam were like something from a horror film. People were “peering into the hedgerow expecting the mother of all spiders to emerge,” says Stuart Hine, a British Natural History Museum entomologist. What was responsible for this spooky mess?

Not a giant, Harry Potter-esque arachnid, says Hine, head of a team that IDs mysterious bugs from around the world. The real culprits were the larvae of flying insects known as ermine moths, so named because their white wings with black spots resemble a certain weasel’s winter coat. The caterpillars create these silky veils when they’re trying to eat enough greenery to sustain themselves through weeks of cocooning and post-metamorphosis life as moths. Hine guesses that in the widely publicized Rotterdam incidents the bugs simply ran out of trees and randomly descended on a car (below). Weird as the giant webs can look, it’s normal for these caterpillars to spin them. The larvae’s feeding seldom causes lasting tree damage, and the adults are useful plant pollinators. And, Hine adds, “Once they’re out of their cocoons, they’re lovely little moths.” —Chris Carroll