The Friends of Charles Darwin

Spotted in my garden last weekend:

Is it a twig, or is it a caterpillar?

Isn't Natural Selection utterly amazing? I would never have spotted this creature had it not, rather stupidly, taken up residence on a fence, rather than the branch of a tree. As a rule, fences tend not to have twigs.

The delay in posting this photo was due to my unsuccessful attempts to identify the species in question. My best guess at the moment is that it is the caterpillar of the world-famous peppered moth—which would be rather cool. Apparently, it isn't just adult peppered moths that come in a variety of camouflaged colours, hence my uncertainty.

I will get to the bottom of this one.