Ant refuse piles are scraps of remains from whatever giant or fire ants were able to prey upon. Usually filled with human and brahmin remains, they are covered in a mucus-like substance and webs.
In Fallout 3, they are usually found in areas that are heavily infested with giant or fire ants.
Fallout: New Vegas
In Fallout: New Vegas, they can be found in areas which are inhabited by giant or fire ants. It should be noted that ant refuse piles can spawn fire ant nectar as well as the normal ant nectar.
Ant Refuse Piles appears in Fallout 3 and in Fallout: New Vegas.