we have little garden snakes which eat the mice I believe, and sun on the boulder by the hives, never noticed any in the hives, however the cat loved to eat them...fascinating behaviour, it makes perfect sense that a small snake would eat larvae, I don't know about hardware mesh though a snake can fit into some pretty small places. Perhaps requeen with some queens of temper.

Im not trying to get my head into any larvae, and I am being whacked daily from one hive that turned evil. I kind of don't mind a mean hive, i always wear a suit now because no matter where I am in the apiary Im in the flight path of some hive that doesn't appreciate it. As far as Im concerned the mean hives are one more insurance policy against nosy bears or other pests. Id love to see that snake if you catch it! Good luck. A mouse trap or sticky paper might be an option...
