Was mowing my MIL's yard with a push mower and ran over a hole without realizing it. Got hit about 3 times and I looked back and saw them swarming out of the hole. Went inside for awhile to nurse my wounds and plot revenge. A half-hour later I went back, fired up the mower and centered it over the hole and kept it there for about 5 minutes. Couldn't see what happened, but suppose it turned them into mulch as they came back out to attack. Didn't see but a couple the rest of the afternoon when they returned from being away from the nest. After reading this thread I guess I was lucky they didn't seem to have another exit.