Patiently and precisely the ants use their sharp mandibles to slice away pieces of green leaf like tailors scissoring a vest from a pattern. When a segment is free of the leaf, the ant balances it in its mandibles, which look menacingly similar to the “Jaws of Life.” One can watch for hours and never see a slip-up, never see a botched cut, never see an ant lose its footing or its cargo flutter to the ground like confetti. Hundreds of thousands of ants, sometimes millions, busy at the same task, as proficient and inexhaustible as an automobile assembly line.

Looking like an armada of Chinese junks sailing across a cluster of leaves and down a branch or vine, the ants head to the same destination: a subterranean city 15 to 20 feet deep. Once in their nest, they chew the leaf fragments and use the mulch to grow a garden of fungus. That part of the fungus called gongylidia is sustenance for the colony. That’s right. These ants are a society of agriculturists. Farmers.

Leaf-cutters belong to the attine group of ants, believed to be the first animals to raise crops, in this case fungus. Some 50 million years ago – an eon or two before man thought to scrape away a patch of earth with a rock and bury a seed – leaf-cutters were already cultivating their next meal.

There are nearly 40 species of leaf-cutters among the 10,000 or so named species of ants in the world. The genus Atta is found in every New World country except Canada and Chile. The species Atta cephalotes in Lincoln Park Zoo’s two colonies (one colony is off-exhibit) are from the island of Trinidad. Each colony contains more than 10,000 ants. In the wild millions of ants maintain a single colony.

You can watch this display of “awesome teamwork,” as one little boy described it, at the Regenstein Small Mammal-Reptile House. “Our exhibits at the zoo try to show visitors the diversity of ecosystems,” says Associate Curator Diane Mulkerin. “They demonstrate how all types of creatures, including some of the tiniest, like ants, play an important part in the balance and the health of the environment.” The exhibit consists of seven viewing windows showing chambers that together resemble the workings of an underground nest in the wild. The chambers are interconnected by tubes off-exhibit, so the ants can travel between chambers. A nest in the wild is a series of complicated trails featuring Y and T junctions.

The first chamber (to the left as a visitor faces the exhibit) is the browse area. Every day fresh foliage from zoo grounds, including Boston ivy, dogwood, wild grape and honeylocust leaves, is placed in the two-story chamber. After the ants cut a piece of leaf, they march to the upper-right chamber, a sort of staging area where they have built a hill of browse. “The hill is at the entrance to the nest, and we think it helps regulate the temperature and humidity,” says animal keeper Matt Campbell. “The humidity in the fungus chamber is near 100 percent. If it was higher there would be too much moisture and that would kill the fungus.

“In the middle of the hill is a hole, which the ants travel down to reach the first fungus garden. There’s also a midden, or garbage dump, in that chamber. Workers carry things like bad browse and dead ants to the midden.” In the exhibit’s next three chambers to the right, the colony is also building fungus gardens, one of which covers an entire window. The gardens look remarkably similar to honeycombs.

Each ant has a specific role in maintaining the colony. Soldiers, at least fives times larger than the smallest ant in the colony, go on trails and watch for predators and often stand guard at the nest entrance. Workers do most of the cutting and transporting, pull sentry duty and serve as garbage collectors, hauling waste to the middens. The smallest ants are the minimas, who distribute the food and harvest the fungus.

Some minimas also ride shotgun for worker ants, perching on the edge of a leaf fragment like a lookout in the crow’s-nest of a ship. They warn workers about the approach of phorid flies, parasitic pests who lay eggs onto worker ants preoccupied with making their delivery. If the parasites were to get a foothold in the crevices of an ant’s segmented body it would eventually die. In the zoo exhibit’s controlled environment, flies are of no concern. While ants can consume more than 15 percent of rainforest foliage every year, leaf-cutters also provide a valuable service by fertilizing the soil with the vegetation they carry down into their nests. It’s a workload they are uniquely designed to perform.

Imagine a weightlifter twirling a 500-pound barbell like a baton while walking across a cable 50 feet above ground. That’s the kind of strength, dexterity and balance leaf-cutters combine when lugging their load up and down, over and around foliage while dodging the constant crush of ant traffic on an arboreal highway. It’s estimated that a typical trip between leaf and fungus garden is equivalent to a human being running 4-minute miles for 30 miles while carrying a duffel bag full of cement blocks.

If you think that sounds like man’s work, in the leaf-cutter ant work world there is no such thing. Females do all the heavy lifting, because there are no males in the entire colony. Every ant – soldiers included – is a daughter of the queen. A typical colony in the wild reproduces itself once a year at the start of the rainy season, with new colonies taking two to three years to fully mature. The new queens can collect up to 300 million sperm, for future use. The males soon die, and the queen burrows herself into the soil, never to return to the surface.