"Keep you mouth closed. You might catch a fly". Like any kid, we'd roll our eyes, but you're the first person I've actually heard of who actually 'caught' a bee. And we had bees for years and never got stung in/around the mouth.
That said, one did get up into my head gear and stung me on the bridge of the nose. Felt like someone hit me with a 2x4 across the nose for a while.