The leaf-cutter ant lives in huge underground nests, connected by a series of tunnels (2). The ants cultivate a special ‘fungus garden’ deep within the nest, and are almost entirely dependent on the fungus for food (2) (5) (9). Maintaining the garden is crucial to the survival of the colony, and worker ants perform a variety of tasks, including foraging for leaves, cutting them into suitably sized fragments, transporting leaf fragments back to the colony, and preparing a ‘mulch’ (made from the leaves), which is used to cultivate the fungus garden (2) (5). Some of the smaller ants ‘hitchhike’ on leaves carried back to the colony, and are thought to protect the foraging ants from parasitic flies (Phoridae), and may also play a part in leaf preparation (7). It is essential that the fungus garden remains free of parasites that could cause disease, which would be devastating to the leaf-cutter ant colony. Microorganisms that have the potential to be harmful to the fungus are removed by some of the smaller garden workers as waste, which is taken to a separate waste chamber, reducing the chance that the fungus, or other ants in the colony, will become infected by harmful pathogens (5) (10).
In a colony, only the queen is able to produce offspring. The queen is capable of laying thousands of eggs per day, most of which are destined to become workers, with only a small number of these developing into males and females capable of reproduction. At the beginning of the rainy season, fertile individuals leave the nest to take part in a ‘nuptial flight’, a single flight during which mating occurs, and after which the males die (2) (6) (11). This is the only time that the females mate, and the potential queens are capable of storing several hundred million sperm, which are used to fertilise the eggs in a future colony (11). A new colony is created by a solitary female queen, who will dig a tunnel, and, using a tiny piece of fungus brought from the old nest inside a special cavity in the mouth, will start to cultivate a new fungus garden and begin egg laying (2) (8) (11) (13). Despite the large numbers of leaf-cutter ant queens that attempt to establish a colony, very few actually survive, with the probability that the founding queen will die before eggs hatch and the fungus garden becomes established estimated at nearly 90 percent (2).