The Vapourer - Orgyia antiqua - Caterpillar.
Very small (~7mm) in a pine plantation forest, crawling quite fast across my bag.
Photo is available for use and distribution under Attribution-Noncommercial-Share Alike 2.0 Generic Creative Commons Licence.
I request that I am informed of any use of the image, so that I can see how and where it is used. Please visit my website for contact details - www.zpyder.co.uk