The feisty shark mamas are back!

Thrilled to  spot this cluster of Giant Willow Aphids when I went to remove a broken bough from one of our tree, I blipped them seven years ago and haven't found them since.

You might wonder why I'm so keen on what's often regarded as a pest.
There are several fascinating points.
1. The adults (which reach 5 mm) have a spike like a shark fin (see extra) on their backs. It's not known what the function of this is.
2. They are all female and reproduce by pathenogenesis. No males have ever been found.
3.They mysteriously disappear in the winter and don't reappear until late summer. No one knows where they go, or why.
4. If something threatens them they all kick their back legs in the air, in fact the biggest mamas can knock a predatory ladybird for six.

What's not to love?

There's more about willow aphids and some great pics  here and here.
Btw, they actually do very little damage. Natural predation keeps the numbers in check.