2 February 2026
While in Costa Rica last month I had several opportunities to watch leafcutter ants marching in long lines and carrying leaves. Their dedication to task was fascinating.
Leafcutter ants are farmers that grow their own food — a fungus — inside their underground nests. They tend the fungus carefully, feeding it freshly cut leaves, flowers or grasses and removing mold and pests that threaten it.
Each of the 55+ species of leafcutters cultivates a particular species of fungus. The fungus thrives because the ants tend it. The ants thrive because their brood eats the fungus.
I recorded two sets of leafcutters traveling to and from their nest. You can hear the voices of other members of our group in my video.
At the nest the entrances are busy with activity (photo from Wikimedia).
Inside, the workers tend the fungus (photo from Wikimedia).
Here are some cool facts about leafcutters paraphrased from Wikipedia:
- Leafcutter ants are endemic to Central and South America and occur as far north at Texas.
- Their nests can contain more than 3.5 million individuals and span up to 6,460 sq ft (600 m2).
- A leafcutter ant can carry up to 50 times her body weight.
- Her jaws have a bite force of 800mN = 2600 times her body weight.
- A colony is founded by one (or more) fertilized queen(s) who starts her own fungus garden from bits of the parental fungus mycelium she has stored in the infrabuccal pocket in her oral cavity.
- The ants and their fungus have a mutualistic relationship. It is so intertwined that it’s best described here: Wikipedia leafcutter ant-fungus mutualism.
- Safety of the foraging line is so important that there is a caste of worker ants that patrol the line to attack any enemies that threaten it.
- A large troop of leafcutters can denude an entire citrus tree in less than 24 hours!
- Worker ants take out the garbage of used substrate, discarded fungus and a parasite that threatens the fungus, and deposit it in a designated area.
- Humans can use the ants’ own refuse to deter them: “A promising approach to deterring attacks of the leafcutter ant Acromyrmex lobicornis on crops has been demonstrated. Collecting the refuse from the nest and placing it over seedlings or around crops resulted in a deterrent effect over a period of 30 days.”
Leafcutter foraging lines are like a living river.