Monday, 26 February 2007

Invasive Ladybird Threatens UK Species

A new ladybird has arrived in Britain. This is not just any ladybird, this is the Harlequin ladybird Harmonia axyridis, the most invasive ladybird on Earth.
There are 46 species of ladybird resident in Britain and the recent arrival of the Harlequin ladybird is a major threat to many of these. It is also a deadly threat to many other insects, including butterflies. The Harlequin ladybird is an extremely voracious predator that easily out competes native ladybirds for food. It is so successful that while native ladybird numbers dwindle the Harlequin ladybird flourishes. When their preferred food, of green fly and scale insects, is not available the Harlequin readily preys on native ladybirds and other insects such as butterfly eggs, caterpillars and lacewing larvae, they are also partial to soft fruit, particularly pears.
Introduced from Asia into North America for biological control of aphids on crops, the Harlequin ladybird has swept across the US, quickly becoming by far the most common ladybird. In the last decade its catastrophic increase in numbers has threatened native North American ladybirds and other aphid predators, many of which are plummeting alarmingly as the Harlequins consume their prey. The Harlequin ladybird is also partial to overwintering inside houses in huge numbers where their defecations destroy upholstery, curtains and wallpaper. Despite this unwelcome and well-publicised take-over of America by the Eastern invaders, Harlequin ladybirds are still sold in continental Europe by biocontrol companies, and it now roams across France, Belgium and Holland, with numbers soaring annually. They were plentiful in St Margaret's last year and have been seen already this year. They are quite variable in colour and pattern: see the Harlequin Survey


tut-tut said...

We have had these "swarm" against the house!

Anonymous said...

That was interesting to read!
I am a retired biologist and I got a feeling, I should have known this :)
but why should I, no need to teach any more, however, I am happy to know
these things!
Perhaps our winter is too hard for this species.