Polyxenus lagurus millipede, (I think, certainly Polyxenus at least!) These 2-3mm long Diplopoda are different to most other millipedes. Others use chemical secretions to avoid predation, but these (like other Polyxenus) use detachable bristles to entangle their predators (ants etc).
View this on my flickr:

Polyxenus Lagurus Millipede

There’s only one place in south west england that I know has these living in the wild annually, information online about them is scarce and the photos aren’t always super clear.

I first discovered these millipedes back in 2010 when I first tried high magnification macrophotography, it took me months to find out what they were. 

Anyone I show the pictures to have never seen them before, nor do they know they even existed.

These millipedes are slightly different to your average - instead of using chemicals to deter predators like most millipedes, polyxenids use bristles on their bodies to entangle predators and slip away unharmed. They’re usually prey for Ants but other arthropods may also feed on them. 
The millipedes themselves eat fungus from fermented bark and lichen.

I’ve only ever found them living in an old wooden joist in someone’s back garden, but they supposedly live in trees, specifically underneath rotting bark.

I really like these arthropods and I’m going to experiment with lens reversal techniques to get an even closer look at them soon. (No, I don’t like using macro lenses - because that’s cheating, right?)