There is a lot of concern these days about invasive species. And rightly so. There seem to be thousands of species out there in the world just waiting to invade. And it’s not just nuisance aquatic species like Didymosphenia geminata (a.k.a. “rock snot,” or didymo for short) and Myriophyllum spicatum (Eurasian milfoil) that are causing trouble in the neighborhood.