Everything about Leafcutter Ant totally explained
Leafcutter ants are social
insects found in warmer regions of
Central and
South America. These unique ants have evolved an advanced
agricultural system based on
ant-fungus mutualism. They feed on special structures called gongylidia produced by a specialized
fungus that grows only in the underground chambers of the
ants'
nest.
Different species of leafcutter ants use different species of fungus, but all of the fungi the ants use are members of the
Lepiotaceae family. The ants actively cultivate their fungus, feeding it with freshly-cut plant material and maintaining it free from pests and
molds. This mutualist relationship is further augmented by another symbiotic partner, a bacterium that grows on the ants and secretes chemicals- essentially the ants use portable
antimicrobials. Leaf cutter ants are sensitive enough to adapt to the fungi's reaction to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is toxic to the fungus the colony will no longer collect it.
The only two other groups of insects that have evolved fungus-based agriculture are
ambrosia beetles and
termites.
Leafcutter ants comprise two
genera —
Atta and
Acromyrmex — with a total of 39
species (15 in
Atta and 24 in
Acromyrmex), some of which are major agricultural pests. For example, some
Atta species are capable of defoliating an entire citrus tree in less than 24 hours.
The
Acromyrmex and
Atta ants have much in common anatomically; however, the two can be identified by their external differences.
Atta ants have 3 pairs of spines and a smooth
exoskeleton on the upper surface of the
thorax while
Acromyrmex have 4 pairs and a rough exoskeleton.
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A mature leafcutter colony can contain more than 8 million ants, mostly sterile female workers. They are divided into
castes, based mostly on size, that perform different functions.
Acromyrmex and
Atta exhibit a high degree of
biological polymorphism, four castes being present in established colonies - minims, minors, mediae and majors. Majors are also known as soldiers or dinergates.
Atta ants are more polymorphic than Acromyrmex, meaning that there's comparatively less differential in size from the smallest to largest types of
Acromymex.
- Minims are the smallest workers, and tend to the growing brood or care for the fungus gardens. Head width is less than 1 mm.
Minors are slightly larger minima workers and are present in large numbers in and around foraging columns. These ants are the first line of defense and continuously patrol the surrounding terrain and vigorously attack any enemies that threaten the foraging lines. Headwidth are around 1.8-2.2 mm
Mediae are the generalized foragers, who cut leaves and bring the leaf fragments back to the nest.
Majors are the largest worker ants and act as soldiers, defending the nest from intruders, although there's recent evidence that majors 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're at risk of being attacked by the phorid fly, a parasitic pest which lay eggs into the crevices of the worker ants head. Often a minim will sit on the worker ant and ward off any attack. (External Link)
In Central America, leafcutter ants are referred to as "Wee Wee" ants, though not based on their size. They are one of the largest ants in Central America; the queen may be larger than a mouse.
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 at work
Image:The stronger of the two.jpg|Two leafcutter ants
Image:Leafcutterperu.jpg|Collecting leaves.
Image:Leaf_cutter_ants_CostaRica.jpg|Leafcutter ants in Costa Rica
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