Giant ant

Giant ants are the effect of nuclear fallout mutating regular ants. What they lack in individual fortitude, they make up for with relentless attacks and swarm tactics. Their exoskeleton isn't particularly thick, but it can turn aside weak punches and dull knives. Their mandibles can cut through most leather and plastic with ease, even snapping bone on a lucky shot. Giant ants become particularly aggressive when their queen is threatened.

Variations
A giant ant species found in Northern California and Oregon lives mainly in dark places, often underground. Areas where they appear include Arroyo and Broken Hills. A stronger variant called a "tough giant ant" also exists.

A larger species of giant ants, with horned-looking skin can be found on the East Coast (e.g. Springvale). They are better adjusted to daylight than their California cousins.

Another rare variation are giant albino ants, found in the Hoover Dam Scum Pits. Their exoskeleton is a very pale yellow that almost looks white, their eyes glow red like the rats, and their mandibles glow green and drip a green, acidic fluid. These ants live in a nest back in the office area and, luckily, are not prolific. But they are hungry, and they do come out fairly often to catch and drag a rat or leech back into its dark lair.

Appearances in games
Giant ants appear in Fallout 2 and Fallout 3.

Behind the scenes
Like many other creatures in the Fallout series, the giant ant draws a large amount from the background lore of old black and white cinema where creatures were mutated into enormous versions of their former selves in unbelievable ways by nuclear radiation.