are likely to perform. Those with the heads about wide tend to work as gardeners, although many with heads wide participate in brood care. Workers need heads only about 0.8 mm wide to do the work of caring for the very delicate hyphae of the fungus, which they care for by stroking with their antennae and moving with their mouths. These tiny workers are the smallest and most abundant and are called minim. Ants of appear to be the smallest workers that cut vegetation, but they cannot cut very hard or thick leaves. Most foragers have heads around wide. Attines, particularly the workers that cut leaves and grass, have large mandibles powered by strong muscles. On average, 50% of worker ants' head mass and 25% of their full body mass is the mandibular muscles alone. Behavior Though all castes defend their nests in the event of invasion, a true soldier caste, with individuals called majors, exists. They are larger than other workers, and use their large, sharp mandibles, powered by huge adductor muscles, to defend their colonies from large enemies, such as vertebrates. When a foraging area is threatened by conspecific or interspecific ant competitor, the majority of respondents are smaller workers from other castes, since they are more numerous, and therefore better suited for territorial combat. Tasks are divided not only by size, but by the age of individuals workers, as well. Young workers of most subcastes tend to work inside the nest, but many older workers take on tasks outside. Minims, which are too small to cut or carry leaf fragments, are commonly found at foraging sites. They often ride from the foraging site to the nest by climbing onto the fragments carried by other workers. Most likely, they are older workers that defend carriers from parasitic phorid flies that attempt to lay eggs on the backs of the foragers. All size groups defend their colonies from invaders, but older workers have been found to attack and defend territories most often. At least three of four physical castes of A. sexdens change their behavior based on their age. Habitat Lower attines mostly live in inconspicuous nests with 100–1000 individuals and relatively small fungus gardens in them. Higher attines, in contrast, live in colonies made of 5–10 million ants that live and work within hundreds of interconnected fungus-bearing chambers in huge subterranean nests. Some colonies are so large, they