A healthy oak eggar moth caterpillar.
A healthy oak eggar moth caterpillar. Soebe/CC BY 3.0

A gruesome plague is infecting oak eggar moth caterpillars in Lancashire, England, and leaving a trail of exploded body parts in its wake. The baculovirus turns the inside of the bugs into goo and brainwashes them into getting up as high as they can. Once the zombie caterpillars are up there, they burst to spread the pathogen below.

Chris Miller, from the Lancashire, Manchester and North Merseyside Wildlife Trusts, was carrying out a butterfly survey in the area when he found “small scraps” of caterpillar hanging from branches and tall blades of grass. “It is really unusual seeing caterpillars high up, as they can be eaten by birds,” he said in a statement. Ordinarily, the larval moths spend much of their time hiding in bark crevices or dirt. The virus, however, reprograms their instincts. “It’s like a zombie horror film,” Miller adds.

The virus “ends up using just about all the caterpillar to make more virus,” Kelli Hoover, an entomologist at Penn State University, explained to National Geographic. “It becomes a pool of millions of virus particles that end up dropping onto the foliage below, where it can infect other moths that eat those leaves.”

So is this the start of the zombie caterpillar apocalypse? Probably not, Hoover says. The virus may actually be a positive thing, ecologically speaking. When moth numbers grow, outbreaks of the infection might help keep caterpillar infestations in check.