Invasion cannibal of the ladybirds

Since arriving from Asia in 2004, they’ve infested homes, spread disease — and now they’re wiping out our beloved native ladybirds...

NOW THE clocks have gone back, we’re seeing all those traditional signs of autumn. Conkers and acorns, leaves turning brown . . . and an army of lethal ladybirds invading our homes.

With winter just around the corner, swarms of multi- coloured harlequin ladybirds are coming in from the cold.

They’re gathering in vast numbers in the cosy corners of our kitchens, bedrooms and living rooms.

Larger than our native ladybirds — and, as their name suggests, a colourful array of reds, oranges, yellows and blacks — they are also killers.

The larvae of the harlequin ladybird are voracious feeders: eating aphids, the young of other ladybirds and even turning cannibal, killing their own larvae.

Harlequins also carry a fungal disease, which is spread when the ladybirds mate and can be fatal for our native species.

Numbers of our most familiar species — the two-spot ladybird, with a pair of black spots on a red background — have plummeted by 50 per cent in the past decade.

That’s especially sad given the central place of these colourful little beetles in our culture. They feature in nursery rhymes — ‘Ladybird, ladybird, fly away home . . .’ — and, of course, there are the Ladybird Books.

According to ladybird expert dr Helen Roy, at least seven of our 25 native species are declining — and it’s all down to the larger, tougher and nastier harlequin.

Yet as recently as the turn of the millennium, harlequins were unknown in Britain. Originally from Asia, they were first spotted in the UK in Essex in 2004.

Known as the world’s most invasive ladybird, the insects arrived in Europe as stowaways on flowers, fruit and vegetables. Having arrived on the Continent, they simply flew across the Channel to Britain.

Others came on fruit and vegetables imported from North America, where the species was misguidedly introduced in the early 20th century to control aphids.

In the U.S. and Canada, they are known as the Halloween ladybeetle, because they enter homes at this time of year in search of a warm place to spend the winter.

They secrete a sticky, protective mucus that could be dangerous for other animals.

DR LINDSAY MITCHELL, a vet in Kansas, recently posted online a graphic photo of a dog that had around 40 ladybirds stuck to the roof of his mouth. dr Mitchell said it was not the first case she had seen and that it could cause long-term issues for animals if left untreated, including ulcers on the tongue and mouth. In just over a decade since harlequin ladybirds reached Britain, these colourful insects have spread all over the country. They are common throughout England and Wales, and have been seen from the Isles of Scilly in the south to Shetland in the north.

I remember first noticing them a couple of years after they arrived, when I found dozens swarming on my office window at the BBC Natural History Unit in Bristol.

My colleagues and I were amazed to see so many ladybirds clustered together in one place. But we had no idea this was just the start of an unprecedented invasion.

Moving north at a rate of more than 60 miles a year, harlequin ladybirds are officially the UK’s fastest ever invasive species.

Each female can produce around 1,000 to 2,000 eggs in its lifetime, laying them in batches of ten to 30 per day. They have spread more than ten times more rapidly than other non-native creatures, such as grey squirrels, muntjac deer and ring-necked parakeets.

Harlequin ladybirds are not always easy to identify. That’s partly because they are one of the most variable insects in the world, displaying a bewildering range of different shades, colours and patterns.

However, they are noticeably bigger than our familiar native ladybirds — being up to one-third of an inch long.

The commonest variety is usually pale orange or red in colour, with up to 20 black spots.

Others are black with just two, three or four red spots. But I’ve also seen ones that are all red or completely black.

These different varieties are very sociable — especially at this time of year. So if you discover a cluster of multi-coloured ladybirds in your home, you know that you’ve been invaded.

The best way to prevent infestations is to make sure your doors and windows are well sealed.

If they’ve already got inside your home, some pest controllers suggest using a vacuum cleaner to Hoover them up.

But be careful, because when disturbed they emit a nastysmelling yellow liquid that can stain carpets and woodwork.

Of course, the harlequin is not the only insect invader accidentally introduced into Britain.

The latest is the Asian hornet, a lethal killer of honey bees. The first confirmed sighting in the UK came just last month, when one was seen in Gloucestershire. Beekeepers are terrified that these predators — which can grow up to 2 in long — will destroy their precious colonies.

The hornets wait just outside the hive and then ambush the unsuspecting honey bees as they go in and out, dismembering the unfortunate creatures alive.

In our newly globalised economy, where produce is imported from all over the world, it’s hard to see what we can do to prevent unwanted stowaways such as harlequin ladybirds hitching a lift.

SO DO they bring any benefits? Some entomologists think that the harlequin may do some good by killing and eating aphids.

There is also a suggestion that larger native insects, such as house spiders, may be preying on the harlequins, helping to slow down their population boom. Much of what we know about harlequin ladybirds — and many other invasive species — comes from members of the public recording sightings and sending them to various conservation societies.

Using the public to track the spread of these unwanted invaders is just one aspect of ‘ citizen science’, and is helping us to protect our native fauna and flora.

So if you spot any harlequin ladybirds in your home, you can take part in the UK Ladybird Survey — it’s a great way to make children aware of the changes happening to our wildlife ( ladybird-survey.org).

As dr Helen Roy points out, these thousands of sightings don’t just help us track the ladybirds’ progress, they also enable scientists to work out exactly how to deal with the next insect invasion.

So, what does the future hold for harlequin ladybirds?

Lured by our warm, centrally heated houses, they will be staying put until next spring.

Then, when the air temperature begins to head back consistently above 10c, they’ll simply spread their wings and fly outside, ready to wreak havoc on our unsuspecting native species once again.