as far as anyone can tell -- nothing while above ground. They've spent the last just-under 17 years burrowing in the ground, eating who knows what under there. Above ground, though, they just are looking for a one-night stand, after which they drop dead.
We've been advised to protect young (leaf-bearing) trees, because the cicadas cut small slits in the branches and lay their eggs inside; this can harm or kill the young trees. However, they will leave flowers, vegetable plants, herbs, etc., alone.
Also, they like maples and deciduous trees, but have nothing to do with evergreens. If youve got a lot of maples (like us), you're in for a treat. Real fun.
Playboy should do a interview. . .