The fire ants of the Capital Wasteland were created by a scientist named Doctor Lesko. The doctor was attempting to return giant ants to their normal size through genetic manipulation and accidentally created the fire ants. Dr. Lesko's ambition was to make the ants exponentially smaller through generations, meaning the offspring is born smaller than its parents for generations to come. But as he reasons, one small tweak of an error has left the ants with a completely different mutation. The fact that Lesko used F.E.V. in his experiments in order to produce a quicker result may also help explain the "error". Lesko further explains in very technical terms that the ants breathe fire by expelling flammable venom from what was their venom sacks, then igniting it with a spark made by clicking their mandibles. He calls this process "pyrosis".
It is not known how fire ants came to be in the Mojave Wasteland, but theories are that their ability to breathe fire has been developed in the same way as the similar ability of fire geckos.
Fire ants have a hard, red-orange carapace that protects their body from environmental factors. They live in enormous underground colonies where they eat, sleep, and mate with the queen. Fire ants are omnivorous, using their pyrosis, which stems from a mutated venom gland, to kill live prey, but also eat what little vegetation they can find, when necessary.
Fire ants like to attack from range with a fire breath attack (which has surprisingly long effective range). The ants seem to have a minimum range at which they could breathe fire. If you get extremely close to the ants, they will constantly try to move backwards, letting off a spurt of flame or two. Additionally, they have a slow turn speed.
If their antennae is hit and crippled, they will become frenzied. Once a fire ant becomes frenzied, it will attack other nearby fire ants and other non-player characters. Once attacked by another ant, the attacked ant will return fire, damaging the attacking ant.
Due to their high fire resistance, fire damage based weapons like the flamer and the Shishkebab will have little effect on them.
Fire ant nest guardian
Fire ant nest guardians are unique versions of fire ant warriors. There are only five of these ants protecting the queen. Doctor Lesko refers to these ants as "The Queen's Quintet".
Fire ant soldiers are the second lowest ranked ant in the fire ant colony. Their job is to protect their area from intruders. They are very aggressive and will attack humans, as well as other creatures on sight. They are relatively easy to defeat at medium levels or with a well equipped low level character.
Fire ant workers are the backbone for the ant community's infrastructure. As the name implies, they dig tunnels and care for the eggs. However, they will attack intruders if they are threatened. They are relatively weak compared to fire ant soldiers.
This ant queen found in the queen ant's hatchery. Like the others in the game she is slow and has a ranged acid spitting attack that does a fair amount of damage. She cannot spit fire because Doctor Lesko's experiment affected only her eggs. The queen has a very high amount of HP and is considered a "boss" enemy in the game.