Up Close and Personal with 100's of Tarantula hawks

Had I known what these were when I was photographing them I would have run a mile. I read that this insect has one of the worst stings in nature. People have committed suicide because of the pain. The small tree/shrub I was next to had literally hundreds of them hanging from the branches.

If anyone can tell me what sort of tree that is I will remember never to plant one in my yard!