Atta sexdens
Temperature
24–28 °C
Humidity
80–95%
Colony size
1,000,000–8,000,000
Queen size
22–25 mm
Worker size
1.5–22 mm
Diet
Care Guide
Atta sexdens is the great Brazilian leafcutter, the species most commonly kept in advanced collections in Europe and South America. The queen is one of the largest in the entire genus at 22–25 mm, and mature colonies routinely reach one to eight million workers. Polymorphism is extreme, with castes ranging from 1.5 mm minims that groom the fungus up to 22 mm soldiers with heads broad enough to cut through tough plant material — or fingers.
Like all leafcutters, A. sexdens lives in obligate symbiosis with the fungus *Leucoagaricus gongylophorus*. Workers cut leaves, flowers, fruit, and even soft bark, transport them back to the nest along well-marked trails, and process them into a pulp on which the fungus grows. The colony feeds exclusively on fungal gongylidia. A newly mated queen carries a tiny starter pellet of fungus in her infrabuccal pocket and tends it through the founding stage.
The sheer scale of this species in maturity demands extensive captive setups, sometimes spanning multiple chambers and several meters of tubing in private collections.
Care difficulty
Expert. A. sexdens is one of the most demanding species available to keepers. The fungus is far more sensitive than the ants themselves, and a single mistake during the founding stage — overwatering, contamination, vibration — can destroy the entire colony.
Housing
A modular system of fungus chambers, foraging arenas, and waste chambers is essential. Maintain temperature between 24 and 28 °C with humidity at 80–95 % around the garden, dropping to roughly 60 % in the outworld. Offer fresh, untreated leaves daily — rose, bramble, oak, hibiscus, blackberry — alongside fruit pulp, soft seeds, and occasional protein such as dried mealworms. Pesticide-treated material will kill the fungus quickly and irreversibly.
First days after purchase
Place the founding queen and her fungus pellet in a small, dark, humid chamber at around 25 °C and leave her completely undisturbed. Do not offer leaves until the first workers are foraging independently. Inspect daily only for mold or contamination, and remove any affected material with sterile tweezers. Founding is by far the riskiest stage; patience here pays off enormously.