Island eradications are always high-stakes, high-wire endeavors — you get, more or less, one big shot at taking out a whole species. Then you wait, sometimes years, to see if the invader has truly been eliminated or has, instead, come back. The coming back from the dead is called the Lazarus effect. Often all it takes is one pregnant female or a breeding pair to undo years of planning and millions of spent dollars. In the ants’ case, one stalwart queen stowed away underground could undo everything Boser had been plotting. ... How do you eradicate tens of millions, if not billions, of tiny insects that live under several dozen square miles of extremely rugged terrain? Killing each ant would be an impossible task. But kill the queen and you initiate a colony collapse, for the queen is the only source of new ants. Only, Argentine ant colonies often boast several queens, so even the ant’s central weakness required a comprehensive plan of attack: Boser needed to poison all the queens at once. If she did that, Santa Cruz would be one step closer to perfection.