During winter break, some adventurous students at the University of Maryland participated in a course that took them on a remarkable adventure to the rainforest in Belize to study Mayan culture and the fascinating creatures and plants in tropical ecosystems. By some strange coincidence, Bug of the Week happened to stow away on this tropical odyssey. Last week in the rainforest we crossed paths with the rapacious army ants in "An army of one million". This week we visit a somewhat gentler, but sometimes pernicious member of the ant clan known in Belize as Wiwis or leaf-cutter ants. In contrast to army ants who are the consummate hunters of the forest floor, leaf-cutters are the farmers in the rainforest. In addition to humans, leaf-cutter ants are the only other animal known to use a living material to cultivate a crop as a source of food. Night and day the workers of leaf-cutter ants search for nutritious leaves of trees and shrubs. When scouts find a good food source, they direct other workers to the bounty by releasing trail-marking chemicals called pheromones. With powerful jaws, the workers clip semi-lunar sections of leaves and carry them to the ground where they join a rambunctious procession of nest mates. In this parade are workers busily transporting leaf sections, smaller workers that sometimes hitchhike on leaves and help defend their sisters from marauding predators and parasitic flies, and large Amazonian soldiers with powerful jaws capable of warding-off enemies. The parade may extend across the forest floor for distances of more than 200 yards as workers carry their leafy cargo back to the subterranean nest. A leaf-cutter nest is a marvelous structure that may contain several million ants and occupy hundreds of square meters of forest floor. Sophisticated ventilation systems cool the bustling nest and allow carbon dioxide to escape while oxygen is drawn in. Once inside the nest, leaves are delivered to other workers that take the leaf sections and clip them into ever smaller fragments. These fragments are carefully inserted into a garden of living fungus maintained by the ants. The leaves serve as a substrate for the growth of fungus that is harvested as the source of food for the ant colony. The fungus garden is carefully tended by workers. Destructive alien fungi are detected and removed. Secretions produced by the queen and workers facilitate the growth of the cultivated fungus. Fungal strands produce specialized structures called gongylidia that are harvested by workers. Gongylidia are fed to the developing larvae and distributed throughout the colony to feed workers, soldiers, and the queen. Due to their agrarian life style, leaf-cutter ants are also commonly called fungus growing-ants. To support their enormous colonies, leaf-cutter ants remove vast amounts of vegetation each day. When nests are established near orchards or crops, leaf-cutters can strip trees and vegetables overnight. Often, their nests are destroyed by farmers.

The wonderful book "The Insect Societies" by E.O. Wilson and the web sites below where used as references for this Bug of the Week. For more information on leaf-cutter ants, please visit the following web sites.

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