Dulcie and our old lab/GSP mix Brandy found out about yellow jackets the hard way while accompanying me on a huckleberry picking trip up in the mountains one fall. I let them run loose in the clear cut with e-collars on to clear out/ repel any bears (and I'd be able to get the dogs back if they decided to get into a hot chase).
The dogs were having a SPLENDED time crashing through brush, eating huckleberries off the bush, running around on logs, etc. while I was picking. Then suddenly they came sprinting in, almost took me out at the knees, and seemed 'stuck' to my legs. ???
I stood up and literally asked the girls out loud "OK, what happened?" They stood there silently and intently looking at me... and suddenly I could see welts rising on their noses, head, and flanks. Question answered, LOL! They hung out close to mom for a little while, looking decidedly deflated.
The kicker was about 20 minutes later when Brandy, the sweet and mild mannered GSP/Lab, suddenly started growling and walking slowly and stiff-legged towards a chunk of brush with a little evergreen poking through. I immediately straightened up from berry picking and yelled, thinking that it could be a bear and I REALLY didn't want to surprise it. No large animal was produced but Brandy kept stalking the chunk, Dulcie sneaking behind her.
Suddenly I noticed a large yellow jacket nest in the tree.