Insect larvae on white oak tree

There are at least a dozen of these clusters on a little white oak tree. I removed one of the fuzzy things from a cluster and found that it contained a green insect larva, firmly attached to the twig. The "hairs" are sticky. I doubt there are many predators for such an unappetizing thing. I showed the photo to my entomologist friend. He said this is a type of gall that is caused by a wasp. The fuzzy things are individual larvae.