Cool Black and White Wasp or Hornet

at the gardens in rockwood park

Oak sapling gall (Cynipidae)

At Bryan Park in May 2015, there were a couple of these things on the end of some low-to-the-ground little oak saplings. They were kind of horrifying. They turned out to be galls. There's larvae in there.

This type of gall is made by a wool sower wasp (Callirhytis seminator).