Atta sexdens is a species of leafcutter ant belonging to the tribe Attini, native to America, from the southern United States (Texas) to northern Argentina. They are absent from Chile. They cut leaves to provide a substrate for the fungus farms which are their principal source of food. Their societies are among the most complex found in social insects. A. sexdens is an ecologically important species, but also an agricultural pest. Other Atta species, such as Atta texana, Atta cephalotes and others, have similar behavior and ecology.
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DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
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NocturnalNocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal",...
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HerbivoreA herbivore is an animal anatomically and physiologically adapted to eating plant material, for example, foliage, for the main component of its die...
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FungivoreTe
TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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PolyandryPolygyny is a mating system in which one female lives and mates with multiple males but each male only mates with a single female.
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EusocialNo
Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
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A. sexdens workers forage leaves up to a range of 60 m from the colony. The scouting workers leave behind a trail of pheromones after they discover a source of suitable plant material. Other workers follow this trail to the leaves. They cut the plant material to pieces suitable for an individual ant to carry back to the colony.
Smaller workers sometimes ride on the leaf pieces while the foragers carry them. The purpose of this behavior is not known for certain, but may be to protect the exposed foragers from attacks by parasitic insects. These insects include flies of the family Phoridae which lay their eggs on foragers. The resulting larvae eat the ants alive.
From late October to mid-December, the A. sexdens colonies produce winged virgin queens and males. Before the nuptial flight, young queens visit the colony's fungal gardens and place a small piece of fungal mycelium in their infrabuccal cavities. During their nuptial flights, the queens mate with several males, which die shortly after. The queen retains the sperm in a special organ for the rest of her life.
It is estimated that each queen is inseminated by 3-8 males and that the number of fathers per colony is between 1 and 5.
The mated queen lands on the ground and tears off her now-unnecessary wings. Then she digs a vertical tunnel to a depth of about 30 cm. At the end of the tunnel, she excavates a small chamber. The queen then starts a fungal garden using the piece brought from her birth colony. Usually, the garden is fertilized only with feces, but sometimes it is necessary for the queen to forage a small quantity of plant material. The queen also lays a few eggs.
The queen then tends to the fungal garden and the developing larvae, feeding them fungus and trophic eggs. The queen herself eats nothing during this period, sustaining herself on fat deposits and her shrinking flight muscles. After the first brood of workers is ready, they take over the running of the fledgling colony and the queen becomes strictly an egg-laying machine. This process takes 40–60 days.
At first, the colony grows slowly, but after two to three years, the growth becomes faster. One possible reason for this is, before the colony is established enough to sustain any large soldier-caste workers, it is useful to remain unnoticed. Soldiers usually appear when the colony has a population of about 100,000. After the number of workers reaches 5–8 million, the colony stops expanding and diverts resources into producing queens and males.
The virgin queens are very rarely successful. Assuming the number of colonies in an area remains constant over time, on average only one queen among the many thousands sent out by a colony successfully founds a new one. However, a mature colony of several million workers faces very few dangers. No known predator, except the mostly subterranean army ant Nomamyrmex esenbeckii, actively attacks the nests, and even other highly aggressive army ants show a healthy respect for an A. sexdens colony. If spared from floods and human activity, the colony is usually destroyed only when the queen dies of old age, giving a successful colony a lifespan of 10–20 years. In that time, the colony will have sent out numerous males and virgin queens to found new colonies.
