Harlequin ladybirds have been declared the UK's fastest invading species, having spread to almost every corner of the country within a decade. First spotted in Essex in 2004, the species has now reached as far as Cornwall and the Shetland Islands, outpacing other invasive species such as grey squirrels and ring-necked parakeets.
Scientists monitoring the spread warn that the harlequin, known as the world's most invasive ladybird, is responsible for the decline of at least seven native species. The two-spot ladybird, a popular native species, has seen its population drop by 44% since 2012, with no signs of recovery.
Dr Helen Roy of the Centre for Ecology and Hydrology noted that public sightings through the UK Ladybird Survey have been crucial in tracking the invasion. While the harlequin is now consolidating its presence, its impact has been less costly than other invasive species like Japanese knotweed, which costs the UK economy £166 million annually.
Despite the threats, harlequins may offer some benefits by preying on aphids that damage crops. Additionally, native insects may be adapting to prey on them. Dr Roy emphasised that lessons from the harlequin invasion could help prepare for future threats, such as the bee-eating Asian hornet.
