We have had serious problems with yellow jackets trying to get into the
hives (only in the fall).  Here in Ohio, I must put on entrance reducers no
later than August 1st because of them.  I did learn one interesting thing
about them.  Yellow Jackets love sugar, but in the fall they actually prefer
protein snacks.  So we bait the yellow jackets traps with a bit of
hamburger.  We also put the full traps in a large Ziplock bag & freeze it
overnight to be sure all are dead before emptying the trap.  Don't want one
of those mean things near my hives!!  Linda in Southern Ohio.