When it comes to venomous ants, few species are more fascinating and vicious than bulldog ants. They have a nasty sting, are very aggressive, and are large enough to be more than a little intimidating. They are so aggressive and territorial that they will even keep fighting after they've been cut in half. In fact, this species becomes something like zombie ants, and when split in two, both halves will try to kill one another.
This might seem farfetched, but bulldog ants, also called myrmecia, are not the only species of ants that attack themselves. The only major difference here is that an individual ant attacks an actual part of itself, in a death battle that can last for many minutes. It's also worth noting that these ants have both venomous stingers, and crushing mandibles, so things can get pretty hardcore.
Believe it or not, there are even more facts about myrmecia ants that make them all the more fascinating. That being said, this is one critter you don't want to mess with, so you're better off just learning about them from afar.