Living on the ice

On a day that was too icy to enjoy walking, I tried some outdoor macro photography. I was hoping for something like the extra, but when I was looking at ice on a tiny weed I was amazed to see through the screen that a small creature was running about. The image is about 3mm wide, so the animal is less than 1mm long and invisible to the the eye.

The camera was preset for photo stacking, with one second exposures, so I was very lucky that it paused while it was in focus. If I'd thought quicker I could have switched the camera to a custom preset I have for wildlife.

Everything on the patio was frozen under a thin layer of ice from an overnight shower, and it was a couple of degrees below freezing. I didn't realise that any small invertebrates could keep moving when it was that cold. Does anyone know what it is? (Not something that had just fallen off me, I hope!)