Rock Houses And Caterpillars

Had a great day out today at Kinver Edge with a few of the AYWMC crew. The Kinver Rock Houses are quite amazing. We 'accidentally' did a 4 mile walk as well (the purple route in case anyone wants to avoid it in future!). There were hundreds of small caterpillars about (see extra), several of which I brought home with me on my clothes, camera bag and even one in my hair. Does anyone know what they might be?