I saw an ant nearly kill a guy in Panama many years ago.
It was a big (like an inch long) ant -we used to call them 50 cal ants (as in .50 caliber).
It bit him on the neck -his neck swelled up so much that it blocked his airway.
Bee sting kits apparently weren't working fast enough, so we had to *hastily* clear an LZ so he could be medevac'd.

Ever since then, I give ants a wide berth.