After my disastrous attempt at trying to track the mite population in my hive I took a closer look at what I was trying to do. The bottom board is slotted, but does not have any method of sliding in a sheet or board that will keep the bees out. I have to build some kind of lid on the trap so that the bees can’t get in.
Online I see a reference to number 8 hardware cloth pretty regularly. It is a wire mesh that has 8 wires per inch, or ~1/8″ gaps. The bees can get through 1/4″ mesh. My hardware stores only sold the 1/4″ in hardware cloth, so I had to fall back to aluminum screening. It feels sturdy and will not get chewed up by insects.
I went with a similar cheap bottom board as before with a single sticky paper sheet tacked down. The lid is a simple 1×2 perimeter with the aluminum screening stapled on top. Nothing pretty, but it fits under the hive and keeps the bees out and the mites in.
I tested it out for a 5 day period under the hive, checking occasionally to make sure no bees were being harmed. It worked well. In 5 days of usage I counted 5 mites on the sheet. My current rate of 1 mite per day will help me keep tabs on what the mite population is doing. Up down or steady, I should have a decent finger in the wind.
I wouldn’t suggest placing this trap out much longer than a week. A lot of little bugs got in there, and the hive is always dropping debris. As it was, it took a magnifying glass with light to really make sure I could tell the difference between a dark spec of debris and a mite.
Lastly as a bonus of sorts, when I pulled the thing out it was covered in about a dozen small hive beetles. Horrible as it is to see them, I was able to carry them away from the hive and smash every one. I wonder if they are attracted to the pollen and other junk left behind by the bees. Could this make a good out-of-hive trap for SHB? Who knows, but I will be sure to observe the hive beetles every time I use this trap.