I made and deployed about a dozen of these around 6 weeks ago...
I call it the "Bottom Board of Death"
I didn't know at the time if they would work at all, but as you can see from the dead beetles in the lower left quadrant that it does at least work to some extent.
As you can see it is a screened bottom board (or inner cover) made of two pieces of window screen with a space between them.
In each of the inner corners there is a small hole (made with a #16 framing nail) big enough for hive beetles to go through but too small for bees.
The idea is that the bees naturally crowd the beetles into corners, the beetles get into the space between the screens and either can't figure out how to get out, or the bees don't let them out, and they die of starvation/dehydration. There is no corresponding corner structure inside of the trap to help the beetles even find their way back to the hole.
The advantages that this design has over other traps -
No maintenance, you could leave it installed all year.
It doubles as an IPM screened bottom board - the small screen holes don't let SHB enter, but still let mites fall out.
It contains no oil, bait, or poison. Oil traps are nasty, and if you don't empty them they could probably cause bees to abscond. Oil kills bees at least as well as it kills beetles. In this trap they just dry up and die.
Other traps rely on the beetles being clumsy enough to fall in - this one takes advantage of their natural tendancy to be crowded into corners by the bees.
I knocked these together - as simply as possible - just to see if it would work at all and to get an idea of what needs to be different. Obviously a finished design could, and should incorporate things like, a convenient way to install a mite count/bottom closure board, and a landing board, and a plug to empty out dead beetles. But at this point I don't really care about those things - I would just like to figure out how to make it better at trapping hive beetles.
Things that I think might make it better at trapping beetles:
The original design has trap entrance holes on both the top and bottom - the idea being that beetles trying to enter the hive from the bottom would enter the trap from the outside (which they probably do) but I suspect that more of them blunder out through those openings than they are worth. Also, when used as an inner cover the bees propolize the holes shut on the inside surface, so they don't work - but it still traps some beetles which are trying to enter the hive from the outside - but not very many. They don't propolize it when used as a bottom board BTW.
I think that the grid structure that funnels the beetles into the trap might work better if it was taller - or it might also work better if there was a small piece of sheet metal (2"x2" maybe) stapled on as a roof over the area where the grids cross. The point of either would be to make it easier for the bees to crowd the beetles into the holes. There also might be a more optimum shape for the crowding area.
Holes in the outside corners might work just as well, and would be a simpler design - I didn't try them this time, because I reasoned (probably incorrectly) that the beetles would find their way out through them more easily. But in retrospect, in a reasonably strong hive the bees would probably hold them in until they starved.
More space between the screens might be better - or worse. It would let it hold more dead beetles in any event.
I would certainly be interested in any improvements that other people come up with.
I wouldn't be surprised if someone else hasn't already done something like this, but I have never seen any such and I came up with it independently. I wish for anyone and everyone that wants to freely use, or modify it in any way they want - For personal, commercial, or retail use. Just don't try to patent (for what that would be worth) anything based upon this design or I will claim "prior art."
This is not going to be any kind of a magic bullet, but every little bit helps. No matter what else you do - weak, queenless, underfed, robbed out, mite ridden, or diseased colonies are going to secumb to SHB in the south. This is just one more arrow in the quiver.