A ladybird is an aphid-eater, so a force for good whether it's a Harlequin or not. Squashing the invaders will make no difference - they're here to stay, and have been for some time, so celebrate the fact that you have ladybirds at all. :)

That is not a Harequin it is a male ladybird beetle. How do I know? I have seen this type mounted over the red spotted female:)

It's listed as Asian Harlequin ladybird, Loosestrife, so it is a harlequin (link below to image) - if you saw it mounted on anything, that might mean its a male, but given the propensity of males across many species of animal or insect to mount anything vaguely resembling a mate, and sometimes something that doesn't even resemble a mate, it may not mean anything much at all... I don't know whether they interbreed with the native ladybirds either, suppose its possible.

http://www.warrenphotographic.co.uk/24798-harlequin-ladybird

I believe they do interbreed which is another reason our lovely little things are at risk.

Ah well, change is inevitable... if something comes along that's stronger, bigger and more adaptable, then whatever was there before disappears. They're still ladybirds, wherever they've come from.

I was thinking of the Harlequin Bug ( Hemiptera ) instead of its Coleoptera namesake. Is this an unwanted newcomer to the UK?

Well, loosely speaking, Loosestrife, yes - they've been here for some years now, and vary enormously in appearance, but its the 'red squirrel' story again - the grey drove the reds out so now they're more or less only in Scotland, so harlequin ladybirds will likely have a similar effect on our indigenous ones. I don't mind too much personally, what with globalisation and everything, all kinds of things get transmitted round the globe these days, whether they fly here or get transported here, its just life doing its thing. What I would worry about getting here are things like Ebola or malaria carrying mosquitoes...

Thank you Bamboo

If we continue to get warm winters (that's what the pundits say they are) then we may well get mozzies. hanks for bringing that up, Bamboo. Just what we all wanted to hear:)

Ah well, Arbuthnot, you know you can always count on me to mention an apocalyptic scenario;-))

Of course I can. Very reliable, that's you.