1) Do the yellow jacket traps actually trap a significant portion
of yellow jackets, or are they just to keep homeowners busy and
lighten their wallets?

I have two at my cabin. They are a simple affair, and one could easily
duplicate them for nearly free. They consist of a plastic mayonnaise jar,
and a lid that has four holes in it. They go in, and can't get out. They
fall into the liquid and drown. Take an old mayonnaise jar, drill four
holes in the top, put in four pieces of tube of some sort, and JB weld them
in place. Or, just be lazy and go buy some.

They sure as heck work. The best bait to use is apple juice. I've tried
everything from beer to root beer to 7Up to orange soda pop. Apple juice is
the best.

And be advised if you're outside where there's yellow jackets, they WILL go
into your cold drink can or bottle. A friend got stung in his mouth. He
was jumping and whooping and hollering, and we were all clapping and
stomping to the rhythm until we found out what his problem was. Now, I put
a plastic cat food lid over my drink when outside, and advise you to do the
same. Clean the lid first.

Steve