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A Caterpillar Invasion Turned This Dutch City Into a Ghost Town

If I asked you to name a silk-spinning animal, your brain would almost certainly jump to something eight-legged. It makes sense; spiders get a lot of attention. They’ve even got their own web-shooting superhero (not to mention, eleventy-seven reboots … plus one). But when it comes to excreting the gluey fabric, no creature can match the power of ermine moth caterpillars. Every now and again, thousands of the tiny creatures show up en masse. It’s an “alien” invasion that begins right here on Earth, and interestingly, it’s happening more and more frequently. gif-gif

The behavior is called “tenting,” and only some species are able to manage it. The clip above was shot in Rotterdam, back in 2009, when a horde of ermine moth caterpillars descended onto the city.

Being a caterpillar is tough: you’re small, you can’t fly, and almost everything wants to eat you. Hell, some organisms prefer to lay eggs on your skin, and let their babies eat you. It’s not an easy existence, but what ermine moth caterpillars lack in size, they make up in numbers. By working together, the animals are able to conceal themselves in a protective blanket. Like a giant invisibility cloak, the veil confuses birds and other predators well enough to keep them at bay while the caterpillars feed.

caterpillar-1-2016-1-20Source:Sylviane Moss/Flickr

caterpillars-2-2-16-1-20Source: Sylviane Moss/Flickr

Ok, that’s fair enough. But what about the car? The only caterpillar that should be gnawing on cars is the D11T.

While some have suggested the Rotterdam bunch mistook the red Honda for food, that is almost certainly not the case. Ermine moth caterpillars eat tree leaves – in this case, the leaves of the Spindle tree – for six to eight weeks, before finally settling down to complete their metamorphosis. An aggregation of this size will devour multiple trees during this time, and therein lies the explanation for the “carcoon.”

As the ermines move from tree to tree, they have to (quite literally) cover their tracks. The defenseless caterpillars can’t just run across the road, and so they keep their protection with them. Everything in their path, from cars, to street signs, to grass, becomes shrouded in white – a scene nicknamed the “walk of ghosts,” after a similar boom occurred in Cambridge.

caterpillars-trees-2016-1-20Source: Wendy Youlton/Flickr

Before you go into a bug-fearing bout of “kill it with fire,” you should know that this is still a rare occurrence – and it could be our fault.

“People shouldn’t be concerned by, as the caterpillars aren’t harmful,” says moth ecologist Dr Callum MacGregor . “The tenting is just part of the life-cycle of these species.”

There are hundreds of known species of ermine moths, and most of the time, they go completely unnoticed. The leading theory suggests that these super-webs form when multiple females lay their eggs on the same plant, in areas where food is scarce (like developments). Further still, it’s possible that climate change is to blame, as the eggs tend to do better over warm, damp winters. It might be an inconvenience but these aggregations are just one more example of how insects are skilled at just about everything they do.

For more photos of this amazing phenomenon, check out the gallery below! 

IMAGES: Wendy YoultonSylviane Moss, Ron Ballonrosso


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