Leafcutter Ants

Here you are, on a vacation to Guatemala. You’re lying on a hammock near the Central American rainforest…when you find ants all over you, coming from a nearby tree. You fall off your hammock, and that’s when you notice the ants are carrying leaves… You think aloud. “They are probably going to eat that stuff!”

You may have a similar experience at several locations in Central and South America, but many species live as far north as Oklahoma. But this insect, known as the leafcutting ant, does not eat leaves. It carries them to its nest and feeds it to a special type of fungus that these ants grow.

The species of this harvest fungus depends on the species of the ant. The fungus “garden” is located deep underground within the ant colony. The average ant nest contains several of these gardens, each with an average life span of about 3-5 weeks.

As leaves reach the nest, they are cut up into a gooey mulch and licked clean of all other fungus spores that may interfere with the growth of the harvest fungus. Licking the leaves also helps get rid of natural antibiotics. Next, in a clean terrace within the nest, the plant matter is laid out and covered with fecal droppings. The fecal matter fertilizes and breaks down the proteins that the fungus cannot. Finally, a piece of fungal hyphae (the growing, nutrient-using part of the fungus) is placed on top of the plant matter. As it grows, a part called the gongylidia (“gong-ee-lid-ee-ah”) of the fungus is fed to the members of the colony.

A colony of leafcutting ants is comprised of several castes. Most of these are female. Males, which are drones, hatch from unfertilized eggs and die shortly after mating with the queen. Drones are considered lazy and inferior members of the colony, since all they do is eat and lie around until they are mature enough to mate. Most colonies have only one queen, but sometimes there is two or three, especially in large colonies. Other castes include minors (“nursers”), medians (“workers”), and majors (“soldiers”) — all of which are essentially workers of different sizes and specialized jobs.

Only queens and drones can mate, and they are the only ants in the colony that can fly. Ants with wings look much like stingless wasps. The queen loses her wings after she mates.

The queen’s job is to lay eggs and found new colonies. When a newly forming queen wants to found a new colony, she takes a chunk of fungal hyphae from a garden and tucks it into a special pocket in her head. Then, she flies away in search of a drone. When she finds one, she mates with it. After she mates, she looks for a suitable spot for a colony and digs her nest. Soon, she starts laying her eggs. A queen may lay thousands of eggs every day!

The first hatched ants immediately begin their work. The workers, which form the largest caste in the colony, strip leaves off trees and take them back to the nest. Trees in the immediate vicinity are usually stripped bare of leaves. Once the workers deposit their leaves, the tiny nurser workers chew them up and lay them down. They also tend the larvae and eggs in the colony. The gargantuan soldiers defend the colony and provide escort to the workers from enemy ants and predators.

Ants, in general, have many enemies. Spiders often come upon them that have fallen into their webs, providing them with a scrumptious snack. “Hunter” spiders are spiders that do not trap their prey, but actually chase it. Anteaters also eat ants, hence their name. There is even an insect called the antlion that builds a trap nest similar to an ant’s. Its nest lures ants to its opening, where the antlion awaits it with gaping jaws.

Ants even fight each other! Despite computer games that depict black ants attacking red ants, ants may very well compete with members of their own species, regardless of color. In fact, it is more likely that these ants will attack their own species since they get food from a common source. This is why soldiers are essential parts of any colony

Let us now turn our attention to the relatives and non-relatives of Atta cephelotes. Termites look and act like ants. In fact, many people think of them as “white ants.” In fact, termites belong to a completely different order. Yet they are incredibly similar in many ways. This phenomenon is called convergent evolution.

The leafcutting ant’s true relatives are bees and wasps. They all have a hard exoskeleton with three distinctive body regions. Paper wasps, ants, and bees all have similar, yet complex, social structures. And if you look at an ant drone or queen, you’d notice that they look remarkably similar to wasps. Several ant species, including fire ants, have stingers similar to those of bees, hornets, and wasps.

The leafcutting ant has one of the most complex social structures in the world, even among its relatives. It carries leaves 30 times its weight — a feat equivalent to a human carrying a bulldozer. Its mounds contain 350 cubic meters of soil, right above an underground city of 3,000 chambers and 4 million ants, the approximate population of Arizona. Needless to say, the leafcutting ant is one cool insect.