I used to get a wasp down the front of my shirt once in a while. They sting once or twice before I can get hold of them and crush them. I usually don't bother to stop. I'll get a red patch the size of a nickel for a couple of hours. I haven't been stung on the bike for a couple of years now though. I've probably been stung while on the bike maybe 4 times total.

Last time I was stung was when I was taking out a nest of wasps in a wall. Right between the eyes. Previously that year I'd taken out a largish wasp infestation in my attic (probably a thousand wasps or so) without incident.