The world’s most invasive ladybird, the harlequin, has caused rapid declines in UK ladybirds, according to a recent report.
The 2-spot ladybird. It suffered the largest declines as a result of the arrival of the harlequin in 2004. © Paul Lund
Seven out of the 8 UK species investigated have suffered worrying declines in distribution and abundance since the arrival of the harlequin ladybird in 2004. The study shows that the 2-spot ladybird suffered the most dramatic decline of 44% in the 5 years following the beetle’s arrival.
The study was led by Dr Helen Roy from the UK’s Centre for Ecology & Hydrology and Tim Adriaens from the Research Institute for Nature and Forest (INBO) in Belgium.
They used data collected by volunteer members of the public, who took part in citizen science projects in the UK, as well as in Belgium and Switzerland. These countries also saw similar declines in native ladybird species.
The harlequin ladybird, Harmonia axyridis, was first spotted in the southeast of England in 2004 and since then has rapidly expanded north and west.
It is a voracious predator and easily out-competes native ladybirds for its preferred food of green fly and scale insects. When these food sources are scarce they prey on native ladybirds and other insects such as butterfly eggs, caterpillars and lacewing larvae.
The harlequin ladybird was first introduced to North America in 1916 from Asia to control plant pests. It is now the most widespread ladybird species on the continent and has invaded much of northwestern Europe.
The 7 species that have declined are the 2-spot, 10-spot, cream-spot, pine, orange, 14-spot and 22-spot ladybirds. The common large 7-spot ladybird remained stable across Europe.
Orange harlequin ladybird
The harlequin has many different colour variants, which can make it tricky when trying to identify them. However, harlequin beetles are bigger. If a ladybird is less than 5 mm (1/5 inch) in length, it is definitely not a harlequin ladybird. The most common harlequin forms in the UK are orange with 15-21 black spots or black with two or four orange or red spots.
Harlequin ladybirds prefer the nightime, as Museum beetle expert Max Barclay explains.‘The harlequin is more nocturnal than our native ladybirds, and may fly to lights or into lighted rooms at night.
'It also can form big aggregations that hibernate in outhouses, garages etc in the autumn, hence an alternative American name of 'halloween ladybird'.’
Britain’s best-loved beetle is in fact made up of 51 ladybird species, although only 29 of these are recognisably ladybirds. They belong to the scientific family Coccinellidae.
The Museum’s large collection of harlequin ladybird specimens includes most of the known colour forms and helps scientists with their identification and research.
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