The harlequin ladybird, officially known as Harmonia axyridis, was widely introduced across continental Europe as a way to limit the population of small sap-sucking insects called aphids. While it was never intentionally introduced into Britain, H. axyridis was discovered there in 2003, and people across the region have been tracking its spread since 2005.
A new review in The Royal Entomological Society's journal Ecological Entomology notes that tens of thousands of people have provided records of H. axyridis and other species of ladybirds, creating an invaluable dataset for large-scale and long-term research. Declines in seven (of eight assessed) native species of ladybird have occurred and have correlated with the arrival of H. axyridis. Research on this species has provided new insights on biological invasions.