The harlequin ladybird, officially known as Harmonia axyridis, was widely introduced across continental Europe to limit the population of pest insects. In Britain, harlquins arrived primarily by spread from mainland Europe, and it is now very common and widespread over most of England and Wales. A new Insect Conservation and Diversity study shows a clear decrease in the numbers of a native ladybird species--the 2-spot ladybird (Adalia bipunctata--on lime trees over an 11 year period in which the harlequin invaded England.
Harlequin ladybirds accounted for up to 70% of all the ladybirds recorded on the trees. They are known to feed on 2-spots at times, and this predation may be an important driver of the changes observed.
"This long-term field study shows just how numerous harlequin ladybirds have become," said co-author Dr. Peter Brown, of Anglia Ruskin University, in the UK. "The 2-spot used to be one of our most abundant ladybird species but is now quite tricky to find. The study shows clear changes in the ladybird community as a result of the harlequin's dominance."