| Leaf-cutting Ant |
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'' Acromyrmex '' '' Atta '' Leafcutter Ants are social Insect s found in warmer regions of Central and South America . These remarkable ants have evolved an advanced agricultural system based on Ant-fungus Mutualism . They feed on a specialized Fungus that grows only in the underground chambers of the ants' Nest . The ants actively cultivate their fungus, feeding it with freshly-cut plant material and maintaining it free from pests and weeds. This is done through a Symbiotic relationship with a colony of bacteria that grows on the ants that protect the fungus. The bacteria evolve along with the mold that would feed on the fungus - essentially the ants have their own portable antibiotics. When the ants happen to bring back toxic leaves, the fungus secretes a chemical that warns the ant not to collect any more of that type of leaf. Leafcutter ants comprise 2 Genera — Atta and Acromyrmex — with a total of 39 Species 1 (15 in Atta and 24 in Acromyrmex), some of which are major agricultural pests. Some Atta species, for example, are capable of defoliating an entire citrus tree in less than 24 hours. Different species of leafcutter ants use different species of fungus but all of the fungi the ants use are members of the Lepiotaceae family. There are two simple ways of telling apart Atta ants from Acromyrmex ants. The first thing you should look for is the number of erect spines on the dorsal (top/back) thorax of the ant. If there are 3 pairs of spines, then it's a Leafcutter from the Genus Atta , whereas if there are 4 pairs of erect spines then it is an Acromyrmex ant. The second way of telling the two genera apart is to look at the gaster of the ant. The surface of the gasters of Acromyrmex ants are tuberculate (that is, rough with many bumps), while Atta ants have smooth gasters. A mature leafcutter colony can contain more than 8 million ants, mostly sterile female workers. They are divided into Caste s, based mostly on size, that perform different functions. The smallest workers tend to the growing brood, while other small workers (head width less than 1 mm) care for the fungus gardens. Slightly larger minima workers (or minims) are present in large numbers in and around foraging columns. These ants are the first line of defense because they continuously patrol the surrounding terrain and vigorously attack any enemies that threaten the foraging lines. Workers with headwidths of around 1.8-2.2 mm are the generalized foragers, who cut leaves and bring the leaf fragments back to the nest. Finally, the largest worker ants are soldiers who defend the nest from intruders, although there is recent evidence that soldiers participate in other activities, such as clearing the main foraging trails of large debris and carrying bulky items back to the nest. The largest soldiers (''Atta laevigata'') may have total body lengths up to 16 mm and head widths of 7 mm! When the ants are out collecting leaves, they are at risk of being attacked by a parasitic fly that tries to lay eggs inside their bodies. Luckily, the leafcutters have ants riding on their necks hundreds of times smaller than they are to ward off any attacks. A leafcutter ant colony with millions of workers is like a large human city in that it produces copious amounts of waste. In order to prevent the spread of diseases and the rise of pathogenic pests in their gardens, leafcutter ants have developed one of the most advanced waste management systems in nature. Waste products from the gardens and dead members of the colony are segregated away from the main nest by specialized "waste workers." Transporters carry the waste to garbage heaps, where other workers who live exclusively in the heap turn over the growing pile in order to accelerate decomposition. The Nests of mature Atta colonies are marvels of engineering, with thousands of underground chambers extending downwards to more than 6 metres in depth. The central nest mound itself may be 30 metres in diameter, and have numerous 0.3 metre diameter feeder mounds extending outwards to a radius of 80 metres. Image:Atta_colombica_queen.jpg|''Atta colombica'', queen with larvae and workers on substrate Image:Atta colombica workers cutting whole plant.jpg|Workers of ''Atta colombica'' cutting all leaves of a young tree Image:The stronger of the two.jpg|Two leafcutter ants Image:Leaf cutters.jpg Image:Leafcutter_ant_on_job.jpg|Leafcutter ants on job Image:Long_way_of_leafcutter_ant.jpg|Long way of leafcutter ant See also
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