I only ride on trails and some of my riding shirts are loose. Back in late May me and a white face hornet decided to occupy the same space at the same time on a trail. I was descending on a longish (maybe 100 ft) technical rocky section. You know, the kind where your butt is behind the seat and takes a bit of concentration. Anyway, the hornet decided to fly up my sleeve, proceeded to sting me six times in the arm pit and me not able to do anything until I got off that section. It hurt to say the least although I was quite proud I maintained enough concentration to keep from wrecking and breaking something. I got to the bottom and jumped off my bike, threw it on the ground, threw my Camelbak, ripped off my helmet and proceeded to tear my shirt off, all in about 3 seconds. My buddy looked at me like I was crazy until he saw the welts, swelling and redness in my arm pit area. That was not fun.
So far I have been lucky that all the bugs I swallow when riding (beetles, moths, gnats, etc) have not been bees!
BTW my bike nose dives under braking too....