So, recently I was told I could use 8 mesh wire for beetle traps. That most beetles would go through 8 mesh. Well, I put that theory to the test. If you are able to see the picture attached you will see on the left the smallest hive beetle I could find and on the right an average size one, at least the ones in my hives anyway. They are sitting on a piece of 8 mesh. Even the small one would have a hard time getting through and certainly wouldn't fall through. The one on the right came from a trap made with 6 mesh wire and I have seen no bees getting through, or at least none end up in the oil.
Just had some time and was curious.