On Monday, my wife discovered that we had a hornet's nest in a tree in our front yard, about the size of a football. Lots of activity. She wanted it gone, so I found in the basement a can of wasp/hornet killer, read the label and went to work. I sprayed it 3-4 times (running after each application). The can said wait 24 hours then remove the nest. Well, my kids were having a good time watching me do this and wanted me to cut down the small branch where the nest was. I got out the ladder and limb cutter, gave it a snip and ran. The hornets were understandably annoyed, but they wasted no time - about 2 minutes after I cut that limb, they had picked out a new spot just up from where I had cut there branch and started on a new nest! I like their enthusiasm.
Mike
P.S. I sprayed the new in-progress nest on Tuesday, will provide a report later on the results.