Small Matters

Millions of years ago, leafcutter ants learned to grow fungi. But how? And why? And what do they have to teach us?

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Possibly the fungi developed tricks to fool the ants into moving and harvesting them. Secretions on the surface of the fungi could function like mind-altering drugs, bending the ants to the fungi’s service. “I think the other fungi are constantly trying to break the chemical codes that help ants recognize their garden fungi, saying: ‘Hey, I taste and smell right! You can’t resist me. Pick me up and take me home,’” Schultz speculates. “Do not underestimate the power of the fungus,” Mueller intones.


Indeed, the very next afternoon, Schultz returns from an outing with impressive evidence of that power. He had come upon a gigantic black ant known locally as a bala—fierce, with a potent sting—clamped around the top of a shrub’s branch. It was rigid and dead. From the back of the ant’s head, a brown sporophore gruesomely protruded, as if in an insect version of the movie Alien. The fungus had infected the ant’s body, growing inside and consuming it. Then, through some kind of yet-to-be-discovered catalyst, the fungus had apparently urged the ant to climb to the top of a branch, where its spores could be spread to maximum advantage. There, a sporophore sprouted through the ant’s head and released its spores.


Back up the trail and in the forest, Schultz ambles, his shirt and pants pockets crammed with vials filled with alcohol. He stops beside a log, kicking off its bark. Out tumble half a dozen Acromyrmex, leafcutters that often build their nests in logs. Below the alarmed insects a riot of brown and tan fungus blooms. “You’d be amazed at how many fungus gardens are out in the forest,” Schultz says. “They’re everywhere.”


Across the hillock, kneeling in the dirt, he spies a tiny dust-colored creature with a wobbling, oversize head. It’s a Cyphomyrmex, among the least studied of the attines. Schultz leans over this creature, no larger than a comma, and observes it carefully.


Fieldwork in the Amazon is far messier than genetic analysis of ant corpses in the comfort of Schultz’s air-conditioned lab back in Washington, D.C. But this is the only way “to experience real, unfiltered biology,” he says. “It’s that complexity that is almost guaranteed to reward you with something you didn’t expect.” Perhaps the Cyphomyrmex will give up one small piece of the puzzle that Schultz and Mueller have dedicated their careers to putting together. In tackling some of the biggest questions in the cosmos, Schultz says as he studies the ant’s meandering gait, it’s best to “think small. That’s what’s great about being out here. Thinking small opens up all kinds of possibilities.”


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