San José, Costa Rica, since 1956

Turning the leaf-cutter ant into an ally

To Costa Ricans, the leaf-cutter ant can be one of the biggest pests to cause severe agricultural decay in parts of the country. To tourists, a trail of the hard-working red insects can appear as a hypnotizing source of amusement. 

To microbiologists, these engaging creatures provoke a more complex fascination.

Found only in Central and South America, as well as in the southern U.S., leaf-cutter ants can devastate farms in tropical regions. 

The ants act as both rivals and role models to scientists. Researchers want to stop leaf-cutter ant infestations from wiping out farmlands. But the ants also hold clues to important puzzles, like how to produce better antibiotics or develop cheaper biofuels. 

“For us, they are master microbiologists,” said Adrián Pinto, 34, a scientist at the University of Costa Rica’s Research Center for Microscopic Structures.

Pinto, who has a doctorate in microbiology from the University of Wisconsin-Madison, in the United States, is Costa Rica’s top expert on leaf-cutter ants. Pinto’s work with the bugs earned him a National Science Award from the Costa Rican government in 2010, the most prestigious award for advances in scientific development. 

In an attempt to best simplify the scientific fascination with leaf-cutter ants, Pinto explained how these tireless workers earned a reputation as the world’s most efficient farmers. 

Leaf-cutter ants don’t eat the leaves. Instead, they place slices of flora into a fungus garden, which they grow with a natural fertilizer. The fungus garden supports up to 5 million ants in each colony. 

Bacteria coexist with the ants. Microbes provide the insect agriculturists with antibiotics that protect the garden, produce nitrogen as a natural fertilizer and assist in breaking down hard-to-digest plant fiber, turning the matter into energy. In colonies, bacteria, fungi and leaf-cutter ants work together as a super-organism that thrives four meters below the ground in 30-meter-wide “city-states.”

However, the systematic insects create problems with their efficiency. 

In Costa Rica, the bugs lay waste to citrus groves, teak plantations, ornamental plant gardens, shade trees on coffee farms and other so-called “cash crops.” Pinto said no figures exist on the amount of damage leaf-cutter ants cause each year, but farmers here fear the insects’ hasty pillaging.

Ants also are marring one of Costa Rica’s most cherished archeological sites. Guayabo National Monument, located in Turrialba, on the Caribbean slope east of San José, hosts the remains of a village that is thousands of years old. The pre-Columbian town has experienced significant damage from leaf-cutter ant colonies, which have hollowed out areas under monuments and caused ancient paths to collapse. 

Pinto intends to create biopesticide based on a microorganism that could infect a colony and annihilate leaf-cutter ants harming farms or the relics at Guayabo. It’s a challenging project since the microbe must be virulent enough to reach the queen that gives life to the millions of ants in the mound. Pinto hopes his lab can release a formula for biological pest management by early 2014. 

At the same time, Pinto and his coworkers are taking advantage of the leaf-cutter ant problem at Guayabo. The microbiologists are arming park guides with field manuals on the species and explaining how the alluring insects can be a source of entertainment for guests. Although scientists hope to remove the ants from the monuments, they hope to maintain the leaf-cutter ants in other areas of the park as an integral tourist attraction.

“What we wanted to do was convert the leaf cutters from a mortal enemy to a strategic ally,” Pinto said. 

He hopes other aspects of his research also will make humanity’s relationship with leaf-cutter ants a critical partnership. Studies at the University of Costa Rica and the University of Wisconsin, both run by Pinto’s mentor, Chris Currie, have led to important discoveries about the insects that could have major implications for medicine and renewable energy.

For example, antibiotics used by the ants have been potent for millions of years, Pinto explained, while the most effective human-made antibiotics only last 60 to 70 years. 

In the field of green energy, researchers struggle to find an economical way to convert plant matter into fuel. Microbiologists believe investigators can look to leaf-cutter ants for help. New research with high-powered electron microscopes shows in detail an innate system that’s ideal for converting plant waste into energy.

The ants have captured the attention of other local research institutes. Rodrigo Gámez, president of the National Biodiversity Institute, wrote in a recent blog post about how nature holds the clues to successful alternative energies.

“Cellulose, the main component of cell walls of plants, is a fiber made from a long chain of linked sugar molecules,” Gámez wrote. “If we extract the sugar, like leaf cutter ants do, we could generate large amounts of fuels from scraps pineapple, banana and many other crops. We learn these lessons from nature.”

Gámez noted that even organizations like the U.S. Department of Energy have built a lab to study leaf-cutter ants’ degradation of biomass.

“People are fascinated just by looking at the ants, and then they find out all the things that are going on,” Pinto said. “Then it really captures their imagination.”

For more information and updates on this, visit and catch live feed from the “ant cam” at the laboratory in Wisconsin.

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