Acromyrmex
Acromyrmex lundi
Nuptial Flight Calendar
Flight months: Oct, Nov, Dec
Care Guide
Delving into the world of higher attine ants, Acromyrmex lundi stands out as a remarkable leaf‑cutting species whose intricate fungus‑farming behaviour will captivate any advanced myrmecologist. This polymorphic ant displays three distinct worker castes — minors, medias, and majors — spanning a size range from just 2.5 mm to a robust 9 mm, while the queen grows to an impressive 16–20 mm (AntWiki). The mature colony can swell to 150,000 individuals, a living city dedicated to harvesting fresh vegetation and nurturing their symbiotic fungus garden. Native to the subtropical lowlands of Argentina, Uruguay, and southern Brazil (Bonetto 1959; GBIF Occurrence Data), the ants are well adapted to warm, humid environments. Their nuptial flights occur in the late spring months of October to December, on warm, humid afternoons following rain (AntWeb; Della Lucia 2011), after which each newly mated queen founds claustrally, relying on internal reserves and a pellet of starter mycelium to establish her nascent fungus garden in seclusion.
Categorised as an expert‑level species, Acromyrmex lundi is suited only for keepers with substantial experience in maintaining high‑humidity, large‑scale formicaria. The principal challenge lies not in ant aggression — though they can defend themselves — but in the delicate biology of their fungus crop. A single mistake in humidity management, exposure to mould, or introduction of pesticide‑laced foliage can cause the symbiotic garden to collapse, taking the colony with it. Moreover, their relentless leaf‑cutting and sheer numbers demand an escape‑proof enclosure and a committed routine of daily fresh plant provision. This is a commitment that rewards careful observation of one of nature’s most sophisticated examples of mutualism, but it is emphatically not a beginner’s ant.
Housing must replicate the humid, breathable conditions of their nesting sites. A dual‑chamber setup works best: a spacious foraging arena connected to a humidity‑controlled nest box where the fungus garden resides. Temperature should be held between 22°C and 28°C, and relative humidity between 70% and 90%, ideally with a gradient to allow the ants some choice. Avoid stagnant air; gentle ventilation prevents fungal competitors, yet drafty conditions will desiccate the garden. The nest substrate need not be soil — the ants will build their spongy fungus mass on a clean plastic or plaster platform — but many keepers provide a thin layer of inert clay aggregate or vermiculite to help retain moisture. The foraging area should include branches, tunnels, and a water source. All materials must be kept scrupulously free of mould spores, and the entire setup must be thoroughly sealed, as these powerful ants can chew through weak barriers.
Diet for Acromyrmex lundi revolves entirely around supporting the fungus garden, which serves as their primary food source. Offer daily a bouquet of fresh, pesticide‑free leaves, flower petals, and soft fruit. Bramble, rose, privet, hibiscus, and citrus leaves are often accepted, while apple slices or grape halves can provide extra moisture and sugars. The ants will process these into a paste, feeding it to the fungus, and in turn consume the nutrient‑rich gongylidia produced by the fungus (Della Lucia 2011). Some keepers supplement with very small amounts of dried oat flakes or pollen, but these are secondary; the critical factor is the uninterrupted supply of clean, varied vegetation. Water is provided by misting the foraging area walls daily or via a drinking station with a sponge, taking care not to flood the fungus chamber, as water droplets on the garden can promote bacterial rot.
As inhabitants of subtropical latitudes, Acromyrmex lundi does not undergo hibernation. In the wild, they remain active year‑round, and in captivity a stable warm regime with consistent food supply will keep the colony thriving through all seasons. Attempts to chill them will only stress the fungus garden and are unnecessary.
The first days after purchase are critical for a founding queen or a newly relocated colony. For a lone queen in a test tube or small founding chamber, provide complete darkness and a temperature of 24–26°C. Do not offer any leaves until the first workers emerge; she is fully claustral and will cultivate her fungus pellet using her own body reserves. Even a tiny scrap of leaf can mould and ruin the delicate early garden. Check only rarely by red light. Once the first pale callow workers appear, you may introduce a single small, fresh leaf snippet; if it is ignored after 24 hours, remove it and try again later. For an established small colony, place the fungus garden in its new nest box, connect the foraging arena, and leave them undisturbed in the dark for 48–72 hours before offering the first leaves. Watch for rapid acceptance: cutting activity usually resumes within minutes of offering suitable vegetation, signalling that the colony has settled. Any sign of garden fragmentation, unusual odours, or workers abandoning the fungus during this settling phase demands an immediate check of humidity and ventilation, as early intervention is key.
