Bees. Always bees. Sting twice on one ride, within a 30 minute period-- one on the thigh, the other on the side of my head (went in the helmet vents.) The one on my head was fine-- no stinger left behind, pain had completely subsided within an hour. The one in my thigh, there must have been a tiny bit of stinger left behind, because I had a red bump that itched for probably a month, and didn't fade away for about 6 months.

I think 4 stings in 2015 (we have a whole lot of orange groves local to us) and just one this year, again, on the top of the head. As far as bee strikes go... oh, I dunno. Hundreds. I came home from a ride one day with two dead bees stuck to the downtube.