Blue mud daubers and other predatory wasps hunt spiders. The wasps sting the spiders to paralyze them and then provision their nests with the spiders. The wasps' larvae feed on the spiders.
I saw the struggle out of the corner of my eye. I actually caught some of it with my camera. When I saw this wasp in the spider's web I wasn't sure who was going to win.
Other spiders have webs at strategic places around the outside of the house where I hope to see the blue mud dauber in action again. For that matter, any solitary wasp busy doing its thing, is something I enjoy observing.