Staple is half the story, but the reference to wool barbs is the other half. I thought I saw something in the nature of a possible polymerization breakthrough that would support the production of longer fibers. I couldn't find that but I did find this and it is surely required reading for biosteel geeks. We are trying to spin stuff which is nowhere close to what comes out of a spider's butt, and have a long way to go in understanding what does. http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0000998