Native ladybirds face being wiped out by exotic invaders spreading north northwards.
The harlequin ladybird, originally from Asia, eats the eggs and larvae of other ladybirds and butterflies, threatening their survival.
Surveys have found them breeding in Northumberland, as well as isolated sightings in the Borders.
Seven out of eight UK ladybird species have declined since the harlequin arrived in 2004.
Dr Matt Tinsley, lecturer in evolutionary ecology at Stirling University, said: “They eat aphids very rapidly, so that means there isn’t enough food for native species.
Harlequins were introduced as a form of biological pest control in America in the 1980s but then spread uncontrollably.
The most common form of harlequin in the UK is either orange with 15 to 21 black spots or black with two to four red or orange spots. They are also slightly bigger than native species.
Dr Helen Roy, head of the UK Ladybird Survey, said: “They are spreading at 100 kilometres a year, one of the fastest-spreading insects worldwide.”
Anyone who sees a harlequin or a native ladybird is asked to report it at www. ladybird-survey.org or www.harlequin-survey.org.