Atta (ant) - WikiHQ

Atta is a genus of ants found in South, Central, and southern North America (including the Caribbean). They belong to the subfamily Myrmicinae. Atta are commonly referred to as leafcutter ants, although that name is shared with members of the genus Acromyrmex.

Atta are notable for their feeding habits. Worker ants gather plant material from around their colony and carry it into the colony's underground chambers. The organic material feeds symbiotic fungi growing inside of the colony, which the ants consume. Atta do not sting, but they are known to be strong biters.

Life cycle

As with all ants, Atta species undergo complete metamorphosis. They emerge from their eggs as a larva, which grows until it forms a pupa. Finally, the adult form emerges from the pupa.

Castes

Adult Atta ants are divided into different castes with distinct appearances and duties.

thumb|Atta cephalotes, [[Wilhelma Zoo, Stuttgart, Germany| left]]

thumb|left|250px|Workers of Atta colombica cutting tree leaves

Workers

Most ants in an Atta colony belong to the worker caste. Workers are wingless females who cannot sexually reproduce. They gather food, excavate the nest, and care for the queen and brood. Mature colonies of Atta ants can consist of millions of workers.

Physically distinct forms have also been recognized within the worker and larva castes. A study of Atta sexdens found that among larvae there are two distinct forms: gardeners/nurses and within-nest generalists.

thumb|A line of Atta workers carrying cut pieces of leaves

Soldiers

The soldier caste is responsible for the colony's defense. Like workers, soldiers are wingless and sexless. While some recognize soldiers as a distinct class, they are often considered a sub-caste of workers. Soldiers appear among lines of workers carrying their leaf fragments. They are recognizable by their conspicuously larger size, more formidable spines, and very large heads. These large heads house the muscles used for closing their powerful pincer-like mandibles on enemies. Soldiers should not be confused with army ants.

Drones

Drones are winged males which are larger than workers and soldiers. They are the only male ants who inhabit the colony, and their sole purpose is to mate with a queen during her nuptial flight or at another time. Drones are fed by workers and do little or no work in the nest. Drones have a lifespan of only 1–2 weeks, much shorter than the queen's lifespan of up to 15 years and workers' lifespan of about 7 years. This is because drones are no longer needed after they mate with the queen.

Queens

thumb|[[Texas leafcutter ant|Texas leafcutter (Atta texana) drone mounting a queen. She has shed her wings after her nuptial flight.]]

The queen plays a major role in both creating new colonies and maintaining the population in established ones. When a queen is ready to mate, she leaves her colony of origin and flies into the air with many drones following her. One or more may mate with her, depending on the species and circumstances. Once the queen has mated, she finds somewhere to begin digging a nest. Inside her nest, she lays a few eggs. These will hatch into workers who will expand the nest. From there, she will continue to spawn workers and other queens. A typical queen lays more than 25,000 eggs per day and 150 million eggs over her lifetime.

Fungus cultivation

Atta workers carry fresh plant material into their subterranean nests, where a specialized species of fungus, Leucocoprinus gongylophorus, grows on the plant material they bring. All the ants feed on this fungus.

Workers also acquire water and nutrients from plant sap they ingest as they cut plant leaves.

If Atta ants become trapped in a collapsed tunnel, they make a tapping sound, and other ants will rescue them.

Predators

Nomamyrmex esenbeckii is an army ant species known to prey on Atta colonies. Birds, bats, and ground mammals feed on Atta queens searching for a nest site after mating.

Evolution

The leafcutter ant genera Atta and Acromyrmex split from a common ancestor about 10 million years ago (Mya). The Trachymyrmex group and Sericomyrmex are the closest relatives to the leafcutters; they split off about 17 Mya.

A study found that emissions of carbon dioxide, or , over soil in which Atta nests were present were 15–60% more than over nearby soil with no Atta nests. At an ecosystem scale, this amounted to Atta nests adding 0.2 to 0.7% more to the atmosphere. and their impact on soil carbon dynamics is expected to increase.

Atta ants can also create gaps in forests with an otherwise closed or unbroken canopy by trimming the leaves of plants in the understory; this allows more light to hit the forest floor. They can also alter the types of trees and other plants in their area by selectively bringing seeds into the underground chambers. If the chambers are not too deep, such seeds can send shoots upward, which reach light and grow into established plants.

Interaction with humans

Defoliation of desired plants

Many people consider Atta ants to be major pests. They can completely defoliate a wide range of ornamental, garden, and agricultural plants. Because Atta ants only eat the fungus they cultivate, they may not be as affected as other ants by common insecticides.

As food

thumb|Atta winged males ("Chicatanas") for sale in [[Oaxaca, Mexico]]

Atta drones are a popular ingredient in Mexican cuisine, particularly in southern states such as Chiapas, Guerrero, Hidalgo, Puebla, Veracruz, and Oaxaca. They are considered a delicacy and are high in protein, so they are often served as a main dish. They may be eaten as the sole filling in tacos. A fan of chicatana dishes in Mexico describes them as "smoky and earthy, with a crunchy texture -- ahumado y terroso, con textura crujiente".

In Brazil, the flying adults of Atta ants (locally known as tanajuras) are highly appreciated as delicacies in several regions. The techniques involving their capture and cooking are considered a part of the cultural heritage of people of the Tianguá municipality in Ceará.

The native Guanes people of central Colombia first began cultivating and cooking the insects in the 7th century. They also used the ants' sharp pincers as stitches. The marauding Spanish conquistadors later adopted the habit.

Popular culture

Princess Atta from A Bug's Life was named after the leafcutter genus Atta.

In the novel Atta, a man is shrunk by a bolt of lightning and befriends an ant named Atta.

Species

Atta bisphaerica (Forel, 1908) - southeastern Brazil
Atta capiguara (Gonçalves, 1944) - São Paulo (state), Brazil
Atta cephalotes (Hairy-headed leafcutter ant) (Linnaeus, 1758) - central Mexico to central Brazil
Atta colombica (Guérin-Méneville, 1844) - Costa Rica, Panama and Colombia
Atta cubana (Fontenla Rizo, 1995) - Cuba
Atta goiana (Gonçalves, 1942) - Brazil (Cerrado)
Atta insularis (Guérin-Méneville, 1844) - Cuba
Atta laevigata (F. Smith, 1858) - Colombia to Paraguay
Atta mexicana (Smith, 1858) - Arizona and Texas (United States) to the southern Honduras
Atta opaciceps (Borgmeier, 1939) - Brazil (Caatinga)
Atta pilosa (Buckley, 1866) - Texas (United States)
Atta robusta (Borgmeier, 1939) - coastal southeastern Brazil
Atta saltensis (Forel, 1913) - southeastern Bolivia, northwestern Paraguay and northern Argentina
Atta sexdens (Linnaeus, 1758) - Panama to northeastern Argentina
Atta tardigrada (Buckley, 1866) - Texas (United States)
Atta texana (Texas leafcutter ant) (Buckley, 1860) - eastern Texas and western Louisiana (United States) and northeastern Mexico
Atta vollenweideri (Chaco leafcutter ant) (Forel, 1893) - Gran Chaco

References

External links

BBC archive video of Atta Leaf-cutter ants
Bristol Zoo factsheet