Leaf Cutter Ants: The First Farmers

Rainforests are among the most biodiverse places on Earth. Millions of years of evolution in these regions have resulted in some of the most amazing organisms ever known to man. Being able to survive in a harsh environment dominated by high temperatures and high humidity is a requirement more than a choice. These conditions promote plant growth and attract many arthropods. Insects are among the most diverse animals in the rainforest.  Butterflies are perhaps the most eye-catching of all with vivid colors and metallic shine, some using these colors to warn off their toxic nature.  Beetles, grasshoppers and leaf insects all munch on the exuberant vegetation with little remorse for the plants they are eating.


But those who visit the rainforest will rarely do so without crossing the path of one of the most laborious species in the world –the leaf-cutter ants. There are 47 species leaf cutting ants. My first encounter with these ants came as no surprise in Costa Rica, where they seem to inhabit almost any land ecosystem except for high elevations above 6,500 feet. You may even find them carrying leaf pieces as you exit the airport terminal towards the parking lot where several trees make up the landscape.


The most interesting fact about leaf-cutters is their ability to farm their own produce- a fungus, to be exact. The pieces of leaves they collect are cut in smaller pieces before inoculating them with the fungus, the only source of food for the ants and their larvae. A well-established colony can contain over 5 million ants, of which most are females. The queen is about 2 inches in length and may live for over 20 years. During her lifespan, she can lay more than 200 million eggs.


These social arthropods are well known for their well-structured society divided into castes. The different castes are defined by size. The Mimims are the smaller workers helping to harvest the fungus and feed the larvae, while the Minors are found along the trails and are in charge of defending the workers from any intruders. The Mediae are larger and are responsible for collecting the leaves and bringing them inside the colony. Finally, the Majors are the largest of all, working as soldiers to protect the colony. They are also known for helping clear the paths used by the Mediae and getting rid of waste produced by the colony. Waste workers are usually left isolated from the fungus gardens to avoid contamination.


So, the next time you come across a trail of leaf-cutters, take your time to follow them, as you will be surprised at how far and large the colony may be. While these may be one of the toughest insects to shoot, you get plenty of opportunities as these guys will be on the move non-stop. Try them the next time to visit any country in Central or South America. There are two species that are found in the U.S. ; they can be found in Arizona, Texas and Southern California.


A mediae carrying a heart-shaped petal back to the colony. Costa Rica.
A mediae carrying a large leaf fragment and a protecting minor.
Leaf-cutters follow pheromone trails on their way to and from the foraging tree
Leaf-cutters live in underground colonies holding millions of ants.
The author and his wife at one large leaf-cutter colony in Costa Rica.
In 2022 we came across a nest colony that was over 35 feet wide. Here's Carolina Villegas posing on top of these massive nest for size reference.