What Are Leafcutter Ants?

Leafcutter ants refer to a group of species from the Atta and Acromyrmex genera. They’re named for their habit of cutting and carrying leaves back to their nest. They collect these leaves to cultivate their fungus gardens.

In this article, we’ll learn more about leafcutter ants as we discuss the following:

• Characteristics of leafcutter ants
• Distribution of leafcutter ants
• Leafcutter ant habits
• Leafcutter ants and their fungus gardens
• Benefits of leafcutter ants
• Are leafcutter ants dangerous?

Characteristics of Leafcutter Ants

Leafcutter ants are relatively large ants. Depending on the caste they can be 2-40 mm (0.07-1.57 in) in length. In terms of head size, they range from 0.7 to 5 mm (0.02-0.19 in) wide. [1]

They are generally dark red or reddish-brown in color.

The leafcutter ants from both genera are anatomically similar. However, they have slight differences that distinguish them from each other.

Those from the genus Atta have smooth exoskeletons and 3 pairs of spines on their backs. In contrast, Acromyrmex ants have 4 pairs and rough exoskeletons.

Habitat and Distribution of Leafcutter Ants

Leafcutter ants are found in the Americas’ arid, semi-tropical, and tropical regions. They live in different habitats including rainforests, deciduous forests, and woodlands. They can also inhabit agricultural areas.

Leafcutter Ant Habits

Nesting

Leafcutter ants nest in the soil. They create complex underground nests with thousands of chambers. Most of these chambers contain fungus gardens. Others are for raising young and housing the queen.

Mature leafcutter ant nests can grow extremely large. They can contain more than a million individuals.

What do Leafcutter Ants Eat?

Leafcutter ants primarily feed on their cultivated fungus. This fungus provides them with nutritious structures called gongylidia which they eat. These gonylidia are rich in lipids and carbohydrates derived from leaves. [2]

Adult leafcutter ants also feed on plant sap.

Colony Structure

Leafcutter ants follow the typical ant colony structure. They have 3 castes: queens, workers, and drones. These castes each have specific functions. 

Queens

Queens are the only females in the colony capable of laying eggs. Their primary role is to reproduce and maintain the colony’s population. 

Leafcutter ant colonies are monogynous. They only have a single egg-laying queen.

Workers

Workers, on the other hand, are sterile females. They dedicate themselves to helping the queen and her brood. They do everything from finding food and nest maintenance.

Leafcutter ants are highly polymorphic. They have 4 different-sized workers with specific roles.

• Majors: The largest workers are the majors. They act as soldiers tasked with the heavy lifting. They guard the colony and clear foraging trails of debris and other obstruction.
  
• Mediae: Following the majors are the Mediae. These workers are generalists that cut and carry leaves back to the nest.
  
• Minors: Minors are the second smallest of the 4 types of workers. They protect the foraging columns and the food source. They continuously patrol the terrain and attack threats.
  
• Minims: The smallest workers are called minims. These ants work exclusively at home. They take care of the brood and the fungus gardens. Some minims also work as garbage collectors which keep the nest clean.

Drones

Drones are produced when the colony needs to expand. Their sole purpose is to mate with virgin queens.

Reproduction

Leafcutter ants reproduce sexually and disperse through swarming. At certain times of the year, winged reproductive ants fly out of their nests to swarm. 

Before doing so, virgin leafcutter ant queens head down to their maternal fungus gardens. There they store a small fungal mass in specialized compartments at the base of their mouths.

Afterward, they meet with other ants from different colonies and mate. After mating, the drones die, and the queens land and shed their wings.

The mated queens then search for a suitable location to start a new colony. Once they find a suitable site, the queen will dig a small hole in the soil, lay eggs, and dump the fungal mass.

They take care of the fungal mass before everything else. They feed it with fecal droplets and unfertilized eggs. They continue to do so until the first workers hatch.

When they do, the queens shift their focus to egg production as the workers tend to the fungus. Queens of mature leafcutter ant colonies can lay around 20 eggs per minute or 28,800 eggs per day.

Leafcutter Ants and Their Fungus Gardens

Leafcutter ants are fascinating creatures. They learned to farm 50 million years ago, way before we had any idea of agriculture. In fact, agriculture has since served as the foundation of their societies. Leafcutter ants rely on ant-fungus mutualism to survive. [3]

They cultivate and tend to fungi from the Lepiotaceae family. Different leafcutter ant species take care of a specific type of fungus. They feed this fungus with fresh leaves and protect it from pests and molds. In return, the fungus provides them with food.

The ant and fungus mutualism has gone on for so long that both parties have become dependent on each other. The fungi used by leafcutter ants can no longer live outside of their care. They too, need the ants to stay alive the same way that ants need them. Hence, mutualism is obligatory.

Benefits of Leafcutter Ants

Leafcutter ants provide a number of benefits including the following:

• Soil aeration: Leafcutter ants actively aerate the soil. This allows moisture and air to permeate the soil and stimulate root growth. It also controls weed growth and integrates fertilizers into the soil.

• Nutrient cycling: By bringing leaf fragments into their nests, leafcutter ants accelerate the decomposition process. The decaying leaves then release vital nutrients and enrich the soil.

• New plant growth: By pruning vegetation, leafcutter ants encourage new plant growth.

See this article to learn how ants are beneficial.

Are Leafcutter Ants Dangerous?

Yes, leafcutter ants can be dangerous. Despite the benefits they provide, they too can be serious agricultural pests. They can defoliate crops and cost millions in losses.

Summary: What are Leafcutter Ants?

To summarize, leafcutter ants are a group of species from the Atta or Acromyrmex genera. They’re known for their ability to cut leaves. They collect and take these leaves to their nests to cultivate fungus gardens.

Leafcutter ants form a mutualistic relationship with fungi to survive. They feed and take care of fungi in exchange for food. In essence, leafcutter ants are farmers.