“LADYBIRD, ladybird, Fly away home, Your house is on fire, And your children all gone.”

I've always thought there was something sinister about this nursery rhyme. Whenever I see a ladybird I think of its home on fire and its babies perishing.

The rhyme is said to originate from the practice of calling Catholics (ladybird being a derivative of "Our Lady") to Protestant services in the 16th century, when priests were burned at stakes for holding Mass. Another theory is that farmers cried out the verse before burning their fields after harvests, in an attempt to protect the ladybirds which reduced pests in their crops.

Now it seems we have a new reason for chanting the rhyme. A recent influx of 'alien' ladybirds has landed in the UK, and the critters are reported to be gathering in homes and gardens across the country. The foreign species - Harmonia axyridis, or Harlequin ladybirds - have distinctive red, orange and yellow markings and pass on a sexually transmitted disease.

"Swarms of alien cannibal bugs carrying dangerous STDs invade British homes," screamed one headline. It's not quite as dramatic as it sounds. The disease doesn't actually affect humans - but it can kill off our native bugs. And since Britain's ladybird population is already dwindling, this could have a significant effect on our wildlife.

The invasion of Harlequin ladybirds, from Asia and North America, appears to be down to a rise in breeding, for biological control of pests, causing them to migrate in greater numbers. Coupled with the mild October, we could be in for an autumn of swarms. Thousands of ladybirds have descended on areas of the south, and the UK Ladybird Survey is urging people to monitor numbers.

Ladybirds have long been regarded as the 'gentle beasts' of the insect world. They're not creepy, like spiders, nor are they irritating, like flies, and they don't sting, like wasps. They remain useful for farmers, saving many plants from aphids.

And they're child-friendly. There's something quite sweet about a ladybird landing on us; as children we would gently blow them and make a wish, so when they flew away our wish would come true.

But as a child I also saw a different side to the ladybird, and all this talk of invasions and swarms has reminded me of it. It was the legendary hot summer of 1976, I was on camping in France with my family and one day, while we were on the beach, there was a strange humming noise and suddenly the air turned red. Out of nowhere came a swarm of creatures; it soon became clear they were ladybirds - and they were starting to bite. They were particularly attracted to yellow, and since my mum had the misfortune of wearing a yellow T-shirt she was quite a magnet. We ran into the sea in a futile escape bid and the ladybirds were soon floating on top of the water, nipping away at our arms and legs. We ran to the car, slamming the doors shut, then squealing as they came in through air vents. Thankfully it didn't go on for long, but while it lasted it felt like being in a film.

That evening we returned to the area for a meal, and were greeted by the rather eerie sight of a mass of red grass next to the beach. The ladybirds were sleeping in the grass, turning each blade red.

It was something I've never forgotten, and it tapped into my fascination with TV disaster movies about insect swarms that were a staple of the Seventies.

The swarm of '76 didn't put me off ladybirds, but it made me very aware of the power and unpredictability of nature, and how it can take us totally by surprise.

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