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leaf cuter ants cahuita national park
 - Costa Rica

Leafcutter Ants

Leafcutter Ants

Hilights

  • Scientific Name: Atta cephalotes
  • Status in the Wild: Common
  • Habitat: Grasslands, Rainforests, Tropical Dry Forests, Woodlands
  • Diet: Herbivore

The term “leafcutter ants” can refer to any one of 41 ant species known for their ability to chew leaves in order to create an edible fungus. These insects fall into two genera: Atta and Acromyrmex, both of which are distributed throughout Costa Rica. It is relatively easy to spot the differences between the two genera: Atta leafcutters boast three pairs of spines and a smooth exoskeleton, while Acromyrmex have four pairs of spines and a rough, almost spiky exoskeleton.

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Leafcutter ants have very powerful jaws that vibrate up to 1,000 times per second, allowing them to slice off sections of leaf. Often, hikers may spot a line of ants hauling huge leaves back to their nest, seemingly defying nature; in fact, leafcutter ants can carry up to 20 times their body weight. Though they are normally non-aggressive, be careful not to step into their path, as their defensive bite is strong enough to draw blood.

Leafcutter ants form one of the world’s most complex societies – populations often exceed three million ants and their nests can grow to almost 100 feet in diameter, covering more than 6,000 square feet. Though their name seems to indicate otherwise, leafcutters do not consume leaves; rather, they carry leaf sections back to their nest, where they compost them into fungus. This fungus is the ants’ only food source, and cannot be produced or survive outside a leaf-cutter ant nest.

Leafcutter colonies are divided into workers with set functions: minims are the smallest, and will tend to juveniles and care for the growing fungus; minors are slightly larger and serve as the first line of defense for foraging ants; mediae are still larger and take on the role of foraging; and finally, majors are the largest ants and act as soldiers, defending the nest and their queen. The colony is home to a single queen who lays enough eggs to sustain the society.

Habitat:

In Costa Rica, one of the most common species of leafcutter ant is Atta cephalotes. This reddish-brown insect is common in open areas and secondary forest throughout the country; it is not uncommon to spot them in populated areas or near the roadside. Acromyrmex volcanus is one of Costa Rica’s lesser-known species. They are found on the country’s Caribbean coast, near Puerto Viejo de Sarapiqui, and exhibit habits very different from other leafcutters. These ants do not cut foliage, but rather forage for fallen plant matter, including leaves and flowers. They often nest in trees, and their colonies only measure about 20,000 individuals.

Reproduction:

Virgin queens and males – both winged – ascend into the air to mate in what is called a renovada. A male leafcutter’s lifespan is short: once he has inseminated a future queen, he dies. After mating, the queens disburse to search for suitable colony grounds. Their success rate is very small, somewhere around 2.5%. For the few that are successful, the sole purpose of the leafcutter queen is to produce enough eggs to sustain the colony. She controls the sex of her offspring, producing fertilized eggs for female workers and virgin queens and unfertilized eggs to create fertile males. Except for producing future mating males, the entire colony is female.

Each egg undergoes a complete metamorphosis, changing from egg to larvae to pupa to adult ant. Adults typically emerge 40-60 days after the eggs are laid. The queen, who can live for more than 20 years, will take between 1 and 5 years to fully populate the colony.

Status in the Wild:

Leafcutter ants are not endangered. However, certain species, such as Acromyrmex volcanus, are little studied, and not much is known about their worldwide populations.