Just saw this video where they talk about attracting ground beetles to hunt the japanese beetles. About 7 minutes in https://youtu.be/TIaYP99MKFM

It looks like you are missing the hollow top and bottom metal plates for that harmonica. On the metal plate they are usually stamped with the brand and key of harmonica which is why its hard to find information about that one. Check out chromatic, tremelo, and octave harmonica tunings to see which yours is. You may need a tuner to identify what notes the individual reeds make. You could also fashion together a metal plate with an opening away from the reed holes to make it more comfortable to play.