● Estero del Yugo, Mazatlán, Mexico [el. approx. sea level] view location in Google Maps » ● 01/24/12 12:23PM sunny, air temp: 24°C / 76°F [IMAGE 2 of 2, also see previous image] Atta mexicana workers often climb to the highest branches of a tree or shrub to harvest the leaves for their fungus gardens. Here we see media (mid-sized) workers climbing back down the trunk of a small tree carrying their freshly cut leaves. [scroll down for additional notes/references] ADDITIONAL NOTES/REFERENCES: Ants of the genus Atta (at least 15 species, all in the New World) can have enormous colonies, often with several million inhabitants. A variety of differently sized worker subcastes comprise "the most complex systems of division of labor known in ants" [Hölldobler & Wilson 2011]. Mid-sized (media) workers are the ones most often seen cutting pieces of leaves from plants and trees, and carrying them back to the nest in long lines. Inside, smaller workers (minors) chop up the plant matter into tiny fragments. Yet still smaller nestmates pulverize the material further, then add fecal droplets. Tiny strands of fungus are then added (by even smaller workers), and the pulverized plant material now acts as a growing medium for the fungus. Ultimately, the very smallest workers tend the fungus gardens, keeping them free of mold and other contaminants. All of the workers are non-reproductive females - winged (reproductive) females and males are produced, and take part in occasional mating flights. The males die soon after mating, and make no other contributions to the colony. The cultivated fungus serves as food for the ants, especially the larvae. Adult leaf cutters probably have much of their nutritional requirements met by consuming plant sap directly, as they cut fresh vegetation. - Pogolumina - Pogonomyrmex Harvester Ants of North America