Any idea how well placing a tray of oil at the bottom with a cover that allows only the beetle to pass? The theory behind it is that the beetle runs away as you work the hive. Since they like to hide in dark places, the black bottom is attractive and so they are caught. I'm trying it for now. I've checked it once and removed about 20-30 beetles, I didn't count, but next time I will.
What do you think?