Some of these molecules are outright poisons, designed simply to kill. But one of the great lessons of coevolution (a lesson recently learned by designers of pesticides and antibiotics) is that the all-out victory of one species over another is often Pyrrhic. That’s because a powerful, death-dealing toxin can exert such a strong selective pressure for resistance in its target population that it is quickly rendered ineffective; a better strategy may be to repel, disable, or confound.
