I got stung by a yellowjacket about 2 weeks ago when I was mowing the yard. They had made a nest out by one of my basement windows. I immediately stopped mowing, got in the car, and bought some wasp killer. Then I sprayed them all and sprayed their nest, too. They died pretty much instantly. It was very satisfying. Then I knocked the nest down and crushed it under my shoe. Then I finished mowing the yard.