"Leiningen Versus the Ants" is a gripping tale of Man versus Nature.

As a virtual plague of voracious, thinking creatures marches toward the expansive coffee plantation of its scrappy owner named Leiningen, a frustrated Brazilian official, who calls the coming of the ants an "act of God," tries to convince him to vacate his home and land. Leiningen contends that he is ready for anything; moreover, his mind is superior to any creatures, and he will defeat them. For "intelligence . . . invariably makes man the master of his fate."

After the official departs, Leiningen assembles his workers and instructs them. Two days later, the army of ants marches upon the plantation with the wildlife ahead of them fleeing in terror. As the ants approach, Leiningen has his system of ditches surrounding the coffee plantation flooded with water. "Unless the ants were clever enough to build rafts, they had no hope of reaching the plantation." Ironically, the ants do create a type of raft with leaves. So, Leiningen has the moats drained and then flooded to kill those in the canals. However, the file of workers is not enough to prevent some of the ants from landing on the other sides of the ditches. Whenever they do, the ants bite deeply into the flesh of the peons, stinging them also with a burning, paralyzing venom. Leiningen screams at the men to jump into the petrol and kill the ants on them. When the ants are finally deterred, the workers shout their joy hysterically.

The next day Leiningen rides along the edge of the ditch. He thinks to himself that he has enjoyed "a thrill out of the fight—a pity that it was already over." Unfortunately, Leiningen has misjudged the ants. As he studies them, he becomes aware of "their power of adaptation, their sense of discipline, their marvelous talent for organization." Later, when he sees the soldiers of the ant army carrying leaves to the edge of the ditch, Leiningen gallops away on his horse and orders the gasoline pumps to the southwest front. He calls his workers together, and he tells them that if anyone does not believe that they can win the fight, they may collect their pay and depart. No one stirs, and Leiningen again feels confident.

After days of fighting this plague of ants that keep coming and can cross the gasoline by climbing onto leaves, Leiningen lights the gasoline. But, even as flames engulf the ants, Leiningen makes another discovery—there is no longer any gasoline in the ditches. Nevertheless, Leiningen realizes that his principle of damming the canals can be useful. For if he can dam the main river, the entire plantation will flood. In this way, all the ants can be drowned. To escape the water, everyone can take refuge in the higher level of the manor house.

To effect his plan, Leiningen must reach the dam and turn the water wheel. So, he covers his tight-fitting clothes and high-fitting boots with gasoline and stuffs cotton into his ears and nostrils. An old Indian gives Leiningen a salve which has an odor intolerable to ants. Thus fortified, Leiningen races against death. The salve seems to help, but when he reaches halfway, Leiningen feels ants under his clothes and a few on his face. Once he arrives at the wheel, he seizes it and strains to turn it, but then a hoard of ants attack him. Nevertheless, Leiningen spins the wheel as he feels the bites of the "sawing and piercing insects."

Remembering how a stag was taken down by these creatures, Leiningen is spurned onward. He runs in desperation and makes it back. The workers come to his rescue on dry land as the ants are repulsed by petrol streaming on them. Later, on his bed in the safety of his home, Leiningen awakens and is informed that the ants are gone. "I told you I'd come back," he whispers.

Leiningen owns a plantation in Brazil. He is an arrogant man and refuses to flee an army of ants marching toward his farm.  They eat anything in their path. He refuses to give up years of hard work  to "an act of God." He gets his workers, tells them about the ants. Though the natives are scared, the remain.  "The ants were indeed mighty, but not so mighty as the boss."  Despite setbacks and being offered dismissal with full pay, none of the men leave Leiningen. They fight the ants all day. Leiningen uses a system of levees, moats and "decoy" fields to fight the ants.  He draws some of the ants off to a valueless fallow field, while keeping a large portion of the others off of the central compound with a system of defensive canals. The ants are initially unable to cross over, but soon manage to build bridges on the bodies of ants who mindlessly sacrifice themselves.  As the bridges of ant corpses begins to reach the near side of the canals, Leiningen opens a series of sluice gates, to increase the flow of water, and wash away the prior ant bridges. He also uses petroleum to burn the ants.  In the end, he floods his plantation, destroying the ants and reducing his plantation to waterlogged rubble and ruined crops. The ants are defeated, but not without great injuries to Leiningen.