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.
[citation needed] A. sexdens colonies are primarily subterranean with a mound of excavated material on the surface.
At the top of the mound are structures resembling sand castles surrounding hundreds of openings to the colony.
As the ant activity and fungal metabolism heat up the colony, hot air rises through the central passageways.
[citation needed] A. sexdens follows the basic body plan of ants fairly closely.
[citation needed] In addition to the queen, the colony contains four castes of sterile female workers, and seasonally some winged virgin queens and males:[4] Considerable variation in size occurs within the castes, some of which may be related to the division of labour.
[6] Their developmental larval stages are observed associated with fungal hyphae, and possess unique morphological features, compared to other ants.
On the contrary, only the most advanced ant societies can expend such lavish care to their offspring as required by Atta larvae.
The scouting workers leave behind a trail of pheromones after they discover a source of suitable plant material.
They cut the plant material to pieces suitable for an individual ant to carry back to the colony.
[citation needed] Smaller workers sometimes ride on the leaf pieces while the foragers carry them.
Leaves and other soft plant material brought into the nest by the foragers is chewed into a pulp and fertilized with faeces.
They also use secretions from their salivary glands and help form antibiotic-producing Streptomyces bacteria to keep their fungal gardens a strict monoculture.
The fungus produces special structures, called gongylidia, which have evolved to be eaten by ants.
Dirt collected by licking is stored in the workers' infrabuccal cavities, which are special recesses in their mouths.
Due to the high concentration of various nutrients in the decomposing waste, a thick net of plant roots usually permeates the compost.
[citation needed] From late October to mid-December, the A. sexdens colonies produce winged virgin queens and males.
Usually, the garden is fertilized only with feces, but sometimes it is necessary for the queen to forage a small quantity of plant material.
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.
After the number of workers reaches 5–8 million, the colony stops expanding and diverts resources into producing queens and males.
This has two important results: The soil becomes aerated with the excavation of tunnels and chambers, and enriched with nutrients as the ants bury their waste products.
[citation needed] A. sexdens and other leafcutter ants are also important herbivores, consuming 12–17% of the leaf mass-produced in neotropical rainforests.
As the local plants have not developed defensive compounds against leafcutters and Africa does not have parasites evolved to infect them, the results for both the ecosystem and agriculture would be disastrous.