AMERICAN signal crayfish are far from Lincolnshire's only non-native invader.

In 2007, experts at the Lincolnshire Wildlife Trust warned that the cannibalistic harlequin ladybird had arrived in Lincolnshire – and now they are endemic across the county.

Harlequins are bigger than most British ladybirds and are known to eat other ladybird larvae and even bite humans.

Japanese knotweed has also become a major problem for gardeners.

Introduced as a decorative plant in the early 19th century, it spread into the countryside, where it can grow a metre a month.

In a more aquatic environment, experts said in February that they expected "chaos and landslides" after the appearance of Chinese Mitten Crabs at one of Lincolnshire's coastal nature reserves.

The large crustaceans, with furry looking bristles covering their claws, burrow into river banks and leave a network of tunnels, which then collapse – taking the habitat with them.