Giant cannibal slugs from Scandinavia are invading back gardens in Cambridgeshire.
The molluscs, which can grow to up to six inches long, appear to be resistant to slug pellets.
Gardeners and allotment holders have complained that the creatures are devouring their prized plants.
Graham Cornell said dozens of the the 'Vulgaris' slugs - sometimes called Spanish Slugs - were living in his back garden in Lode, Cambridgeshire.
"I’ve never seen anything like them," he said. "They’re huge and they leave a trail behind them half an inch wide."
"They don’t seem to be affected by pellets - the only way to stop them is to spear them."
"Luckily, I’ve finished growing many of the things in my garden so they haven’t done as much damage as they might have done."
Mild weather this year is thought to have allowed their population to flourish after it was pegged back in 2010 by cold weather and morning frosts.
They are known to feed on dead mice and even other slugs - as well as other garden foliage.