The initial idea was where you cut the top off of a plastic water bottle, invert it and seal it back up. Put something sugary inside and they'll be attracted to it, but won't be able to get out. Tried this, but only about four ever went in.
I figured I needed a way to cover their nest entrance and funnel them into such a trap. Here's what I came up with.
And boy did it ever work!
This one water bottle, and the top of another water bottle. Both attached to a plastic container that comes with salad or spinach leaves or something, with two holes cut into it. All taped up together.