Noticed a few more ladybirds around your house and garden lately? You might also have noticed they’re bigger than the ones you’re used to – and have black wings with red markings, rather than red wings with black spots.

If so, it’s likely they’re Harlequin ladybirds, and according to some recent newspaper headlines, they’re ‘invading the UK’ and spreading ‘STDs’!

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So what’s really going on, and what can you do if they’re turning up as unwelcome guests in your home? We spoke to Dr Chris Terrell-Nield, Principal Lecturer in Ecology and Nottingham Trent University’s School of Science and Technology to find out:

How has this ‘ladybird invasion’ come about?

This isn’t the first year we’ve talked about Harlequin ladybirds. In fact, as Dr Terrell-Nield notes, they’ve been here about 12 years, with early sightings dating back to 2004, in Essex. “It’s one of these rather sad biological control stories, really, they come from the Far East originally, brought over to Europe as a biological control for pests on crops - things like aphids,” he explains.

“But they were never introduced to the UK. They basically flew here from the Continent, and since then they’ve spread to cover really the whole of England and Wales and bits of Scotland.”

[Read more: Invasive insects swarm Cambridgeshire home for three days]

Is it true they’re a threat to native ladybird species?

“They can be, yes. Like all ladybirds, they’re very predatory, and they’re also a big ladybird - about the same size as a British seven spot ladybird, and that’s one of our biggest ones - and they eat the larvae of smaller ladybirds. They particularly affect things like two spot ladybirds.”

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Why is this a concern?

The UK has around 40 species of ladybird and they play a part in pest control in gardens and for crops. “And this invader comes in and basically upsets the system by destabilising existing populations,” notes Terrell-Nield. “[The Harlequin] likes certain habitats which the others don’t necessarily tend to inhabit. So it can live somewhere they can’t, and also overflow into their habitats and displace them.

"It could have quite a serious impact on our native ladybird diversity. It’s probably the most invasive ladybird there is and spreads quickly. It also spreads a fungus when it mates, and if that gets out of the Harlequin population into the British ladybird population, that could be an issue.”

What about in our homes and gardens?

Harlequins are also quite fond of soft fruits, so those with orchards or fruit trees or bushes in their gardens may notice their presence. They’re especially visible at this time of year. “In the autumn, it hibernates and clusters, and comes into houses or outhouses to find conditions where it can hibernate over winter,” says Terrell-Nield.

"They’re normally found in the corners of window frames,” he adds, noting they tend to prefer cooler homes rather than very warm ones.

[Read more: 10 of the bugs and insects that will be living in your house this winter]

Should I be worried if they’re in my house?

“Essentially, they’re harmless to people,” says Terrell-Nield, but he acknowledges they’re probably unwelcome, and advises against handling them.

“In general, people don’t like to see a cluster of insects in their houses! Even such nice things as ladybirds, which have got a lot of good press over the years; there’s lots of rhymes about them being helpful for crops and so on,” he says. “The problem with Harlequins, like with other ladybirds, when you disturb them, they bleed. It’s not really blood, it’s a kind of yellowish fluid [which comes from their mouth] and that can stain fabrics and furnishings and so on. That’s a defence reaction they have.”

They bite too – but generally only if you handle them and it’s “hardly more than a pin prick”, however, as with everything, some people might experience a more sensitive reaction.

So how can I get rid of them?

If you want to avoid yellow stains – and nips – it’s best not to handle them.

“Use a dustpan and brush, or a Hoover if you really want to get rid of them, and let them go outside,” says Terrell-Nield. “In terms of a species, they’re here, and they’ve spread pretty far and there’s not much you can do which won’t seriously affect other ladybirds - which we don’t want [to happen].”