I watched a wasp drag a Neoscona spider across the sand for a long distance. After passing a small bush, it was ambushed by this Black Widow. They fought tooth and nail (so to speak) for quite a while. I took video of the whole thing that I will post a link to some time later. Anyway, the Widow won but not without a valiant fight by the poor wasp.
I posted the videos to youtube but this link will take you to Part 3, the biggest battle (best viewed full screen):