In the 70 years since the imported red fire ant sneaked into Mobile aboard a ship from Brazil, no insect has been more vilified or subjected to such a relentless chemical assault from Southern homeowners, gardeners and farmers. Even the government joined the quest to kill the pest, but through it all, the fire ant has not merely endured, but prospered, expanding from its original beachhead in Alabama to populate 320 million acres in 18 states. Every year as the weather heats up, Southerners notice anew the earthen mounds of Solenopsis invicta rising like the pyramids of some ancient city,...