Britain's most invasive insect

The harlequin ladybird ,Harmonia axyridis, is a very recent British resident. Originally from Asia it was first spotted in 2004 in a pub garden in Sible Hedingham, Essex. In just four years it has spread across England and made inroads into Scotland and Wales. By comparison it took the grey squirrel a century to do the same.

The Ladybird’s has been tracked by the Harlequin Ladybird Survey, an online survey overseen by the Centre for Ecology and Hydrology. Peter Brown, of the centre, said: “It’s the most invasive species in Britain. It is perhaps equalled by the horse chestnut leaf-miner* but nothing else comes close.”

Last month the species was reported in Orkney. So serious is the problem that the ladybird is the subject of a special issue of the journal BioControl. More than 50 scientists from Europe and North America contributed to the journal to share knowledge about its impact.

Because it eats so many aphids, its staple diet, as well as other ladybirds, it has threatened the number of native ladybirds and species, such as lacewings, which also eat aphids. It also threatens aphid numbers. The two-spot and seven-spot ladybirds are particularly threatened. The harlequin ladybird’s voracious appetite for aphids attracted interest in its use as a biological pest control but after it was released in several European countries in the 1980s and 1990s it rapidly became established and spread widely.

*The horse chestnut leaf-miner is an insect first seen in southwest London in 2002. It has spread rapidly and now infests about 20 per cent of horse chestnut trees, causing leaf loss.