Instructions
Stay a few feet away from the fire ants at all times. The only way the ants can attack is by breathing fire at a target directly in front of them. If you maintain a safe distance of a few feet, the ants will not be able to attack you.
Use a ranged weapon, such as a gun, on the fire ants. This allows you to maintain your distance. As the ants will move towards you as you are attacking them, continue to back up as you fire any shots.
Enter the VATS targeting mode by pressing the right bumper button on your Xbox 360 controller.
Select the fire ant's head from the targeting system. Targeted shots, in addition to head shots, do extra damage on a target, and are the quickest way to dispatch fire ants.
Use any spare Ant Nectar if the ant is close enough to do damage. Ant Nectar provides fire resistance, causing the fire ant's attacks to do less damage. Ant Nectar is found from the bodies of defeated ants, both regular giant ants and fire ants.