An uninvited guest from central Asia – the harlequin ladybird – is wreaking havoc across Britain munching our own species into extinction. PETER FROST investigates
INVASION of “the killer ladybirds” — that was the Sun’s screaming headline and if that wasn’t lurid enough how about this leader from the same paper — “Foreign ladybirds riddled with sexually transmitted diseases are coming to Britain and could kill off native bugs.”
Isn’t it good to see the Murdoch empire taking such a responsible and carefully considered attitude to issues of the environment at last?
In our house it was my wife Ann who spotted them first: “There are hundreds of ladybirds on the curtains in the spare room,” she told me, “but they are not the usual bright red ones.”
It is true, we are under attack from an invasion of harlequin ladybirds (Harmonia axyridis) — originally a native of Kazakhstan and other parts of Asia — who now pose a serious threat to the native ladybird species here in the British Isles.
Harlequin ladybirds have wings with more black than red and they particularly like warm domestic houses and outbuildings and have a habit of clustering together in large groups in suitable areas.
Large gatherings of them can give off a curious chemical smell.
It has taken them just 10 years to outnumber every one of our 47 native ladybird species. The grey squirrel took a hundred years to outnumber our native red squirrel.
The harlequin was deliberately introduced to North America in the 1980s where they were sold as biological pest control against aphids (plant lice) that were feeding on crops, particularly hops and grape vines.
It quickly spread, uncontrolled, across the US to become the most common ladybird there.
It first arrived in Britain in 2004 — some were wafted here on strong arm winds, others arrived on imported plants. They were first seen in Essex and one colony in a Derby supermarket was traced to imported Canadian vegetables.
Since then they have spread as far afield as the tip of Cornwall and the Shetland Islands, making it the fastest alien invasion of Britain on record.
Previously it had spread just as fast across Europe where it was introduced from North America for aphid control in horticulture — they were initially popular with French and other European vine and hop growers.
However, wine growers soon discovered that when any of the ladybird’s bodies were gathered at harvest and pressed with the juice the toxic chemicals in their bodies could spoil the taste of the wine.
Since their first arrival the British native two-spotted ladybird population has declined by as much as a 44 per cent. Every other species of native ladybird has declined too.
The harlequin is regarded as the most invasive ladybird species on Earth. It’s larger and more aggressive than any others, it carries stronger toxins than any of the nearly 50 types of ladybird which are native to Britain and has also been known to eat rivals.
Its diet consists of lacewing larvae, butterfly eggs, moths, pollen, and caterpillars, not to mention our own native ladybirds being eaten to the point of extinction.
These insatiable creatures also cause considerable damage to pear trees, soft fruit and sweet peas.
At the top of their food chain, harlequins have no natural enemies in Britain — they secrete a foul-smelling, toxic substance that deters any bird from eating them.
Over 100 different colour patterns have been recorded which makes them difficult to identify — it is most easily confused with the seven-spot ladybird, which is also variable.
Unlike most other ladybirds, the harlequin doesn’t stick to one type of food. Once it has finished feeding on aphids in the crops it then turns its attention to other ladybird eggs and larvae and even the eggs and caterpillars of moths and butterflies.
The main threat to our native ladybirds comes from their voracious appetite that helps them to easily out-compete native ladybirds for food. In extreme cases wild birds suffer too as their usual diet of small creatures is devoured in the process.
They pose another major threat to our native species because they carry Laboulbeniales, a fungal disease passed on through mating. The disease can infect our native species which are already under threat from habitat loss and overuse of pesticides — the disease, however, cannot be transmitted to humans or domestic animals.
Although they are not dangerous to humans they do hibernate in large numbers in houses and other buildings and tens of thousands of them being are being found in homes during the winter. Such huge groups can be disconcerting or just plain terrifying.
Unfortunately, there’s no easy solution to the problem. Like many other cases of invasive species we think we are much cleverer than nature but good old mother nature somehow contrives to bite us in the bum. While we are on the subject of bites, it is true that ladybirds do bite humans and worst offender is — you guessed it — the harlequin.
If hot dry weather causes their normal aphid diet to shrink they can switch their attention to humans in their search for liquid refreshment.
Environmental scientists are trying to find a solution to the harlequin problem but a quick fix seems very unlikely.
What you can do to help is to report any sightings to the UK Harlequin Ladybird Survey at firstname.lastname@example.org