An amorous Spanish slug is invading Britain and mating with native species to create "superslugs" which threaten to ruin gardens and crops this summer, experts fear.
The six-inch long cannibal, which breeds at twice the pace of its British cousins, is immune to common control methods and can eat up 20 slug pellets without being harmed.
Known officially as the Arion vulgaris, it is classed in the top 100 invasive species in Europe and alongside crops they have been found eating dead mice, dog mess and even each other.
The slugs, which are believed to arrive on salad leaves, were first spotted in the UK in 2010 but were wiped out by cold weather.
Now not only are they munching their way across the country, but it is feared that they are mating with native species to create "superslugs" which can survive in both hot and cold climates.
Leslie Noble, from the University of Aberdeen, said any Anglo-Spanish hybrids are highly fertile and could breed the native species out of existence.
He said: "When they hybridise, the British native slugs get swamped by the invasive genes. It's like adding a large amount of white paint to a black pot. It starts to go grey and eventually, if you add enough, it goes white."
If you're wondering where the spanish slugs are..... They're now this size and will be growing up fast! pic.twitter.com/uXS0K2HZfV— Ian Bedford (@DrIanBedford) May 22, 2015
The Arion vulgaris produces more slime than normal slugs, making them less attractive to predators such as birds and hedgehogs and are more resistant to diseases.
When the two species mate, their offspring have what is known as hybrid vigour, or heterosis, the strongest characteristics of their parents.
Tristan Maclean, a scientist from the John Innes Centre for plant science in Norwich, warned that they could pose a problem to Britain's farming industry.
"I think the big concern is that potentially they could spread across the country and maybe take on some of the traits, if they hybridise and combine with native slugs that give them frost tolerance," he said.
"They produce lots of slime to cope with warm conditions and if they breed they will be able to cope with colder conditions as well. We're looking at a slug that can really effect food security."
Dr Ian Bedford, head of entomology at the John Innes Centre, said "It's about understanding your enemy. "We know so little about this species. We think they're spreading through Europe, and causing problems for crops, but it's all anecdotal at the moment, so we need to do research.
"We've only been able to confirm Arion vulgaris is in East Anglia so far. It is possible it has spread wider afield but without a taxonomic analysis we cannot say."
Dr Noble said that the best way to kill the slug was to put out a saucer of beer as they are attracted to it and then drown in it. "Home brew is the best, but it's quite labour intensive" he said.