This is a bad ant.
At least as far as I'm concerned. I seem to be allergic or "sensitive" to these ants. One bite can become a swollen black lump the size of a half-dollar and with a red bulls-eye in the center. And it hurts like the devil when it bites! I still don't know what it is. I call them "oak ants", because they are commonly found under oak trees. This one was by my lanai. Beware!