Two-spot ladybird populations halved by harlequin
15 May 2012
Seven out of eight British ladybird species are now less commonly seen after eight years of being out-competed by the non-native harlequin ladybird (Harmonia axyridis).
A new study by an international team of ecologists used thousands of ladybird sightings collected by the public in the UK, Belgium and Switzerland to confirm widespread suspicions that the larger harlequin is having a serious impact on native ladybirds across Europe.
The two-spot ladybird, once common throughout Britain, is particularly badly affected with populations now just over half what they were in 2004 when the harlequin was first recorded in the UK. Only the seven-spot is holding its own: the researchers believe this may be because it is a relatively large species which is not in as much direct competition with the harlequin for habitat.
'Within the insect world ladybirds are as iconic as panda bears,' said the report's co-author, Tim Adriaens from the Research Institute for Nature and Forest in Belgium. 'The arrival of the harlequin could impact on the resilience of ecosystems and severely diminish the vital services that ladybirds deliver.'
Introduced to the US from Asia in 1916 to control plant pests, the harlequin has since spread rapidly and now colonises much of north-western Europe. It has many variations in colour and spot number but can be distinguished by its size - 5mm or more in length - and its habit of flying into lighted rooms at night and, in autumn, congregating in large groups in sheds and garages to hibernate.