Ladybirds swarm UK homes as baffled Brits given reason for 'invasion'

Brits have been left scratching their heads as swarms of ladybirds have been spotted gathering by windows and invading homes.

Social media has been buzzing with comments about the harlequin ladybirds - a non-native species - with many wondering what has happened and why they are "everywhere". A user wrote: "I don't know what's going on but there's loads of ladybirds outside casually swarming around my house!" while another said: "Ladybirds, everywhere! Is this the equivalent of flying ant day?".

But experts are urging us not to panic and the sudden surge in sightings can be explained by ladybirds' annual autumn migration as they seek shelter ahead of the colder months.

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Prof Helen Roy, from the UK Centre for Ecology and Hydrology, told the Manchester Evening News: "Winter is a tough time for ladybirds in Britain and so during the winter months they become dormant.

"Each species has a favoured place to spend the winter – some such as harlequin ladybirds enter buildings while 7-spot ladybirds tuck themselves under leaf litter. At this time of year they are moving around to find a good place to overwinter. On warm early October days many ladybirds will be seen flying around in search of a winter habitat."

Warm, sunny spells in early October can trigger the insects to start flying in search of somewhere cosy to spend the winter, which is why so many are being spotted around the UK this week.

And the ladybirds' instinct to find warm, sheltered places often leads them indoors. Max Barclay, Senior Curator of Beetles at the Natural History Museum, said in a blog post: "There are a number of species of ladybirds that hibernate in big clusters. Ancestrally harlequin ladybirds would probably have hibernated in big clusters in caves, hollow trees and other sheltered places."

Without these natural havens, the insects may attempt to squeeze into our properties through tiny openings around poorly sealed windows.

And people are being advised not to harm the ladybirds. "Perhaps gather them gently into a box and put them in an outbuilding if they are in the way but, otherwise, just leave them where they are if possible," said a blog post from the UK Centre for Ecology and Hydrology.

Harlequin ladybirds are not native to the UK, they arrived in the country in 2004 and originate from eastern Russia, China and Japan. These insects are remarkably versatile and display numerous colour variations, ranging from orange with black spots to nearly black with red spots.

While they can harbour parasites and illnesses – including a sexually transmitted disease – specialists emphasise they pose no threat to people. "[The STD] is a fungus that forms little scales on the wing cases on the outside of the ladybird," Mr Barclay explained. "You can actually see it with your naked eye and so can tell whether the ladybird is infected. It just looks like a yellow crust on some parts of the ladybird's exoskeleton."