Ants do follow scent trails - the lavender oil that Freda mentioned would have the effect of obscuring any trails already laid down, and making it difficult for new ones to be created across the lavender oil barrier. Brilliant idea. But what about grasshoppers? I have a house full of them, they're getting into every possible crack and crevice and coming inside, where they inevitably die, one way or another. Happens every spring. So what deters a grasshopper?