KEY POINTS:
An invasive ladybird is threatening hundreds of insect species and other organisms as it rapidly spreads across Britain.
Although it arrived in Britain only in September 2004, it has made a solid start on the process that entomologists have feared - ousting the native ladybird species.
Three weeks ago Britain's leading ladybird expert Professor Michael Majerus of Cambridge University surveyed three central London parks and found the harlequin (Harmonia axyridis) had already taken over to an astonishing degree.
In Hyde Park, Regent's Park and Battersea Park Gardens, 90 per cent of the ladybirds were harlequins, Professor Majerus said.
Before their arrival there would have been a mixture of about 10 species, headed by the familiar two-spot ladybird, but now the harlequin was overwhelmingly predominant.
The UK arrival of the harlequin, an Asian species artificially introduced into the US and continental Europe to control aphids on crops - aphids are many ladybirds' principal food - was greeted as a disaster by Professor Majerus and other experts.
Found in a variety of colours but often orange with black spots (or the other way round), it is a larger and more voracious creature than any of Britain's other 45 ladybird species, and has shown itself capable of outcompeting all rivals and driving them to scarcity and even extinction.
In the US, where it was only found to be breeding in the wild in 1988, it is now the commonest ladybird (or ladybug, to use the American term).
It is thought to have arrived in Britain from the Netherlands, where it was used as a biological pest control. About half the British species - the ones that feed mainly on aphids - are thought to be at severe risk from its depredations, as the harlequin will simply out-eat them: a harlequin larva may eat 500 aphids, but an adult female may eat 5000.
Furthermore, it may not only out-eat them; it some cases, it will actually eat them.
But it doesn't stop there. Professor Majerus has now calculated the "knock-on" effect of the arrival of the invader and he thinks that as many as 1000 further organisms may be at risk of serious damage.
Even birds might be at risk, he said, such as wrens, which were major consumers of aphids.
The harlequin also swarm in vast numbers, often settling in houses.
Professor Majerus does not offer much comfort to householders. "I expect we will soon be seeing cases of swarms of thousands or even tens of thousands in British houses," he said.
"What can you do about it? Say rude words. You can vacuum them up, but when you do they will "reflex bleed" - they discharge this yellow stuff from their knees, which gets all over your carpets and curtains. A strong insecticide will kill them, but do you want that in your home?
"There is a recommendation on one US website that you paint your house in dark colours, especially purple, because when they go to over-winter they seem to be attracted by pale surfaces. Really, all you can do is hope for the best."
He added: "It's certainly one of the most damaging invasive species Britain has ever had, right up there with the coypu, the grey squirrel and the mink."
- INDEPENDENT
