TWIL #048 - Leafcutter Ants Have Been Farming the Same Fungus for 50 Million Years
Leafcutter ants don't eat leaves - they use them to grow a fungus that they've been cultivating in underground farms for longer than humans have existed.
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- #biology
- #nature
- #ecology
Leafcutter ants (Atta and Acromyrmex species) cut and carry leaf fragments back to their colonies - but not to eat them. The leaves are substrate for growing fungus (Leucoagaricus gongylophorus), which is the actual food source for the colony. This agricultural system evolved approximately 50 million years ago, making it one of the oldest known examples of agriculture on Earth. Humans began farming around 10,000 years ago.
Scale of the colony:
- A mature Atta colony can contain 1 to 8 million workers across 4–5 distinct morphological castes, each suited to a different task (cutting, carrying, gardening, defence, reproduction).
- Underground nests can extend 8 metres deep and span over 30 metres, with hundreds of fungus-growing chambers connected by ventilated tunnels.
- Leafcutter trails can stretch hundreds of metres from the nest. Workers cut trails through undergrowth, and the traffic on major trails resembles a managed highway.
The fungus relationship:
- The ants cultivate only this one specific fungus, which no longer exists in the wild outside ant colonies - it has co-evolved with the ants to produce nutrient-rich swellings called gongylidia that the ants harvest and feed to larvae.
- The colony also produces antibiotic secretions from bacteria living in glands on the ants' bodies, used to protect the fungus garden from parasitic moulds (particularly Escovopsis). This is a tripartite mutualism: ants, fungus, and bacteria, all dependent on each other.
Physical capability: Workers carry loads of 10–50 times their own body weight over distances of hundreds of metres. Scaled to human proportions, this is roughly equivalent to carrying a small car.
Queen lifespan: The founding queen can live 15–20 years - one of the longest lifespans of any insect.