For those of you who may be confused, let's use the following formula to determine the level of caution needed for yellow jackets.
1 honeybee = 1 sting
1 yellowjacket = lots of stings /forums/images/graemlins/shocked.gif
In my opinion, yellow jackets are one of the worst. They often net inside something (including ground), are very aggressive, and are small and hard to see (as opposed to large hornets).
BTW- When you squash a yellow jacket, they leave a chemical scent on whatever they were in contact with (shoe, board, etc), which sends any nearby yellow jacket into hyperactive "Defend and Attack" mode.
Bees also attack based on carbon dioxide (CO2), which we all breathe out when we exhale. Don't ever blow on a bee or nest- this marks you as an immediate target.
Breathing only through the nose (Better yet, a hankerchief), and not near nest helps you get closer. Vibration, noise, and adrenaline also set them off.
Good luck, and keep your mouth closed when around bees. Okay, grit your teeth if stung, but don't open your mouth. That's how many people die by bee stings.
-JC