Chapter 6 excerpt from Jack Ewing’s book, Monkeys Are Made of Chocolate: Exotic and Unseen Costa Rica

About thirty years ago Diane and the kids lived in an apartment in San José, and I traveled back and forth between there and Hacienda Barú each week. The guy who lived in the apartment upstairs was a mycologist. That’s a fancy word for someone who knows everything about fungus. Jesse grew mushrooms for a living. He used to bring home bags of fat, juicy mushrooms and share them with all the neighbors. Since I love mushrooms about any way you can prepare them, I have always retained a pleasant memory of Jesse.

Before making his acquaintance it never occurred to me that it might be difficult to grow mushrooms. After all, they are just a fungus and this is a hot, humid climate where fungus goes wild. It grows really well in places where you don’t want it, like on bread, fruit, binocular and camera lenses, VHS tapes, and between my toes. You can’t get rid of the stuff. Growing it is easy; keeping it under control is the problem. Anyway, that’s what I thought. But Jesse told a different story.

I can’t remember all the details because it was a long time ago and the process was very complex. The mushrooms were grown in hothouses where temperature, humidity and ventilation were carefully controlled. This was in the 1970s before the computer age, but for that time, the equipment he used to control the environment around the mushrooms was very sophisticated. The medium where they were grown was cow manure, specially prepared and tested to make sure that the pH was correct and that it wasn’t contaminated with bacteria or other types of fungus. Minerals and other nutrients were added.

Contamination was the most serious problem. I remember a time when Jesse’s mushrooms had become infected with something or other. He was a nervous wreck, getting up in the middle of the night to go out and check on the mushrooms and generally driving his wife crazy. He was like a mother with a sick baby, but his baby was a fungus. Growing mushrooms was far from being the piece of cake I had imagined.

Leaf-Cutter Ants: Nature’s First Farmers

Living near the rainforest and learning its secrets tends to change the way you look at things. One of my major learning experiences with regard to nature’s wonders was when I discovered ants that cultivate fungus for food. You may know them as parasol ants or leaf-cutting ants. They have been doing what Jesse does for around fifty million years and they do it with only the tools provided by Mother Nature.

Atta cephalotes is the most common species of fungus-growing ants in this part of the tropics, but there are close to 200 species throughout the Americas. With a very elaborate social structure and communication system the Atta ants are considered to be one of the most highly evolved of the fungus growers. Daily they accomplish feats that are almost beyond human comprehension. So, let’s have a closer look.

Leaf-cutting ants harvest more foliage than any other group of animals in the neotropics. They utilize around fifteen percent of all the green matter produced by the rainforest. A large colony of seven or eight million ants will consume as much green matter as a cow, but much of this foliage is not eaten directly by the ants. They do consume some of the plant juices, but the more fibrous parts of the leaves are fed to a fungus, which breaks it down into more basic nutrients.

The ants then eat the fungus, which is their primary food source. Only one kind of fungus will work for them, and DNA testing has determined that the fungus the ants grow today is genetically identical to the one their ancestors cultivated fifty million years ago when these early agriculturists began developing their skills. They have kept it pure by not allowing it to fruit and propagating it only by cloning.

On the Trail of Leaf-Bearing Ants

Many of us have seen green columns of leaf-bearing ants marching through the forest, across our lawns, or through our gardens. Some of us have followed those trails and found that it is not unusual for the leaf cutters to walk as far as two city blocks, climb to the top of a tree as tall as a ten-story building, cut pieces of leaves and flowers and carry them all the way back to their colony.

Unfortunately, some of us have also learned that leaf cutters have a special affinity for anything new that we plant in our gardens. If we plant something that is not native to Costa Rica they will usually strip it of all foliage in a very short time. A few of us who simply must investigate further have noticed that, although most of the ants appear to be about the same size and shape, there are a few that are much larger than the leaf carriers, while others are much smaller and often ride on the leaf crescents being carried by their sisters.

To learn more about these fascinating creatures, we must have a look into the writings of those who have delved deeper into the world of Atta cephalotes. I owe much of my knowledge about the fungus growers and the information I share with you here to the extensive writings of E. O. Wilson, Bert Hölldobler, Erich Hoyt and G.C. Stevens.

Complex Systems for Tiny Creatures

In order to deal with the problems of cultivating their particular kind of fungus, Atta cephalotes have evolved their own complex system. You could say that the ants bring the fungus into their homes. They build an underground colony which, on the average, consists of about 1,500 chambers connected to one another by tunnels. The smallest chambers are the size of your big toe and the largest the size of your head. Some are used for living and resting quarters, some for waste disposal, some for brood production, one is for the queen and others are for fungus production. Ideal levels of temperature and humidity must exist in the fungus production chambers. To accomplish these objectives and fulfill their needs, the ants build their city in a very specific way.

Continued in Chapter 6…

[Photo by Riccardo Oggioni]

Read more about the fascinating world of leaf-cutter ants in Chapter 6 of Monkeys Are Made of Chocolate: