Asian gypsy moth: Maine’s female gypsy moths don’t fly, they walk, which makes them somewhat easy to contain when they have a cyclical outbreak and decide to chomp through miles of hardwood trees’ leaves. (Herbicide is spread on the ground; they won’t walk through it.) Asian gypsy moth females fly: big problem. Other problem: They’ve got an appetite for twice as many tree species. How close: West Coast

Asian longhorn beetle: Black and an inch long, the female bores into hardwood trees, lays an egg and covers the hole back up. The little guy wakes up and starts eating. It could threaten maple syrup, lumber and tourism. Scientists sometimes track them by chewing sounds. How close: New York

Mute swans: Twice the size of Canada geese, with the temper to match, they don’t share water well. They’re big eaters and harass native ducks. State officials have been watching a pair that live on the Salmon Falls River on the Maine-New Hampshire border, covertly coating their eggs with oil every year so they never hatch. Massachusetts, with no plans to discourage them, has 500 mating pair. How close: pretty darn

Zebra mussels: From Eastern Europe and thumb-nail sized, they’ve created havoc in the Great Lakes over the last 15 years. Fast reproducers with few predators, they’ll grow in thick clumps, clog waterways, machinery, pipes and pumps. How close: Picked off a boat about to enter N.H. waters in June

Water chestnuts: With saw-toothed leaves and “fruit” below the surface that’s covered in sharp barbs, it spreads quickly, creating a dense mat on the water surface. Can interfere with swimming and boating, and is painful for the inexperienced hand to remove. How close: Massachusetts

Chinese mitten crab: With little sprouts of hair on its claws, the crab’s burrowing can increase shoreland erosion, it can damage nests and it can serve as a host for the people-disease Chinese lung fluke. It’s a traveler, found in Californian parking lots, swimming pools and airport runways. How close: West Coast

Parrot feather: A close cousin to Eurasian watermilfoil, it was meant for aquariums and outdoor aqua gardens, and escaped. It’s got white flowers and grows up to 12 inches above the water’s surface. It can choke out existing water life, and more bad news: provides good habitat for mosquito larvae. How close: Connecticut

Sources: Departments of Environmental Protection, Inland, Fisheries & Wildlife and Agriculture; Washington Seagrant Program; invasivespecies.gov