Nasty little buggers, ain't they.
I was driving to work some years back, down an old country road in CT, when something hit my hand at the window. I looked over in time to see a yellow jacket sting me between the fingers.
I casually took the next road, got on the highway and headed straight to the emergency room about ten miles away. My arm was the size of my thigh in less than five minutes. Thankfully, I don't get the throat issues or breathing problems but I really should carry the epi-pen...