They sponge off the generosity of their hosts like a house guest that never goes away. Other species literally invade the mounds of less aggressive ants, kill the residents, and take over. But whatever the difference, ants truly are much more varied that we ever suspected. One thing that makes ants so important to us is their sting. First of all you should realize that not all ants sting.
Many ants have no sting at all, while other have only mild stings.
While there are actually several native species of fire ant, the imported fire ant snuck into our country around Mobile, Alabama back in the 1930's. The ant uses their mouthparts to get a good grip, then injects a special poison using a stinger. This poison is a type of mild acid called formic acid. Ants use formic acid to kill prey and defend their mound, but they're not the only ones to use it. It's the same stuff used by bees in their stingers as well as the chemical found in the thorns of a bull nettle.