Beauty is in the eye of the beholder is a proverb which means that different people have different ideas of what is beautiful.
This joke is a play on the words beholder and bee holder, which sound the same.
If someone has a bee in their hand, they could be called a "bee holder". The joke is that they have beauty in their eye, because: "Beauty is in the eye of the bee holder" which sounds like: "Beauty is in the eye of the beholder".
beauty is in the eye of the beholder - Wikitionary