A virus is driving a breed of caterpillar on a march to its death after which it explodes to infect other insects.
Scientists have found that across the West Pennine Moors in Lancashire, the skins of Oak Eggar moth caterpillars which had been infected by a baculovirus.
It infects its larvae and changes its instincts to switch from avoiding sunlight to climbing to the top of plants.
Chris Miller, mosslands manager for the Wildlife Trust in Lancashire, Manchester and North Merseyside, said cases had also been found in Winmarleigh Moss, near Garstang.
"It is really unusual seeing caterpillars high up as they can be eaten by birds. This is a caterpillar of the Oak Eggar moth, which eats heather and bilberry, so it is normally hidden in the undergrowth, not at the top of plants," he told the Lancashire Telegraph.
"It's like a zombie horror film...It's pretty gruesome when you think about it".
Scientists in the US recently discovered the way the virus controls the grub.
Dr Jim Slavicek, from Penn State University, Pennsylvania, USA, said: "Who knew that a virus could change the behaviour of its host? Maybe this is why we go to work when we have a cold."
A Wildlife Trust spokesman said: "We would ask everyone who sees caterpillars, or snails for that matter, high up on leaves to report it to us. People should remain vigilant and look out for them."