You are describing the behavior of a spider wasp (family Pompilidae), possibly a member of the genus Priocnemis, although there are others that match this description. These wasps feed on ground nesting spiders. They entice the spider from its burrow, sting it then drag the spider to a burrow that has been previously prepared by the wasp. The wasp lays a single egg on the spider and leaves the stunned spider to be consumed alive by the maggot like wasp larva. The flicking of the wings is characteristic of this group of wasps. It is as if they are keeping their flight muscles warm as they hunt on the ground. I do not know the story about the Orb weaver parasite, but it is probably just one more of the nearly unbelievable tales from the world of insects and spiders. If you ever track that one down, please share it with me (and the rest of the eNature family).
