What species is this grey insect with red antennae and mouthparts?
It's some type of Reduviidae, or assassin bug - possibly a juvenile wheel bug.  Here's a few pictures of Floridan assassin bugs I've found just browsing the net:

Tagged as unidentified Reduviidae from Tallahassee

Tagged as assassin bug

Tagged as a Wheel Bug

Tagged as a wheel bug nymph

Bottom line:
Not an ant, for sure: it's almost certainly in the family of Reduviidae, possibly the subspecies of Arilus cristatus.