What term is used for large worker ants?

The term used for large worker ants is "Soldiers." Soldier ants are a specific caste within some ant species that are larger than the regular workers. Their primary role is to defend the colony from predators and threats. They possess stronger mandibles and often partake in aggressive behavior to protect their nest.

Scouts are a different category; they are typically workers that venture outside the nest to find food or resources and help communicate new foraging spots. Females refer to the reproductive members of the colony, which typically include queens and are not specific to the worker caste. Workers are the primary labor force within the colony, responsible for various tasks within the nest, but they do not refer to the larger ants that specifically serve a defensive role. Hence, "Soldiers" is the correct terminology for those larger worker ants that are tasked with protection.