A tree in Yorkshire, UK, has been overtaken by a giant web spun by thousands of caterpillars. The result is terrifying as the tree is so infested with moth larvae that it appears to be moving, according to local police officer Rich Sutcliffe.

Moths usually construct silk cocoons over food supplies to protect these from predators. On Twitter, PC Sutcliffe, wrote, “I've seen some mysterious sights at work but this took me by surprise today. The entire tree was moving with caterpillars. The caterpillars were literally covering every branch and the trunk of the tree.”


Though they look like webs, the silk sheets are spun by bird cherry ermine or hawkmoth caterpillars. As the larvae grow, the webs extend further, covering several meters. The silk sheet protects caterpillars as they chrysalis into moths and provides shelter as they feed before pupating in the summer.

The bird-cherry ermine is a day active lepidopteran from the Yponomeutidae family. Their wingspan ranges from 16 to 25 mm. Bird-cherry ermines live in bird-cherry trees and can eat a whole tree bare. These caterpillars can be found in Europe and the northern and eastern part of Asia. Hawkmoth caterpillars are medium to large in size and have stout bodies. Some larvae dig into the soil to pupate, remaining there for two to three weeks before emerging as adults, while others, as is the case in Yorkshire, pupate off a host plant.

Swaths of webbing can be seen across bushes and trees in the UK in late spring and early summer. A Butterfly Conservation spokesperson told the Daily Mail, “The caterpillars create these giant communal webs every spring as a protection from predators. You can literally have tens of thousands of the caterpillars inside them. They do this in the spring because at this time of year the new leaves first come out and these are what the caterpillars feed on. The silken webs are enlarged as the food plant is consumed.”

“There are eight species in the group and probably the most likely species is the bird-cherry ermine which has a more northerly distribution. They appear in May or June and can look really dramatic with swathes of webbing across hedgerow trees,” he added.

Though the webs and caterpillars can be frightening to encounter, they are harmless. Paul Kingston, who photographed the webs, said, “It truly was a weird and wonderful sight. It was like something out of a fantasy novel or horror film. It is absolutely incredible to think that such tiny creatures are capable of creating something so huge and beautiful.”

According to Dr. Phil Sterling, a leading moth expert, “It’s an amazing spectacle to look at, like something from a vision of the future, with all the branches completely covered in this ghostly silk.

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“This type of moth loves cherry trees. They eat all of the leaves and once all the food is gone they move elsewhere. The silk is for protection and also where they form their chrysalises. They leave a trail of it wherever they go and are able to use the silk as paths to move forward and backward along. When we see the silk in such large quantities and stretching out around the base of the tree, it is usually because the caterpillars have eaten all of the food and are on the move somewhere else to find more.”