Chicken Little, Chicken Little, the sky is falling. There's a snakehead in my soup. Or is it a cicada? Not since the great hydrilla scare 20 years ago has the Washington area been gripped by a natural crisis of such worrisome proportions. And two at once!

Folks in Bethesda are putting up netting to protect their shade trees from the invasion of noisy insects, as if cicadas were somehow bad for trees, while Maryland officials earnestly tack wanted posters on docks along the Potomac deputizing anyone who catches a dreaded snakehead to kill it immediately by "cutting/bleeding or freezing."

You remember hydrilla. It was the noxious, invasive submerged aquatic weed introduced into the river in the early 1980s by well-intentioned government officials hoping to restore plant life to the troubled waterway. It worked all too well as the weed spread like, well, a weed around the Wilson Bridge.

The media went wild. Hydrilla, we were told, could choke the river from shore to shore in a mat so thick you could walk from Georgetown to Arlington. It would drive out native species and clog our water intakes. It was clingy and could drag unwitting swimmers and water skiers to untimely graves. The stuff was pure poison.

It took a couple of years to discern that hydrilla was about the best thing to come along since dissolved oxygen. As it spread, it stabilized the river bottom, helping other native plants take root. Resulting stands of bright green vegetation clarified and oxygenated the water, provided habitat and food for fish and birds and turned the tidal Potomac below Washington into one of the best urban fishing and birding rivers in the world.

I remember canoeing out of Belle Haven Marina when hydrilla was at its peak and staring over the side at a veritable underwater jungle, full of life. I was with a fellow who liked to hunt for carp with bow and arrow, and while he scanned the gin-clear water for his quarry I dreamily watched the underwater world drift by in little pockets of bluegills, minnows, bass and bugs.

Sadly, the grass has since declined, though holdout patches remain. Meantime, government officials all across the Chesapeake watershed mourn the continuing loss of submerged vegetation and its onerous effects on aquatic life. Last year alone, we learned last week, 30 percent of tidal grass beds in Maryland died because of unusually high runoff from our polluted urban landscape during a rainy spring and summer.

Now there is something to worry about. But snakeheads? Cicadas? Give me a break.

For the record, the snakehead crisis to date centers on three, 12-inch-long fish caught in the Potomac this spring between Alexandria and Woodbridge. One may have been slightly larger but officials aren't sure because its head was hacked off by the nervous angler who caught it.

Since Maryland officially owns the Potomac, it is stuck with the snakehead problem. Steve Early, assistant director of the state's Fisheries Service, is the point man and has been busy answering questions and posting posters. Kill, kill, kill, say the posters. "We don't want any live ones floating around," says Early.

He's worried because the last time northern snakeheads turned up in Maryland, it was in a pond in Crofton where someone deposited a pair purchased at a live seafood market in New York. The pair did the snakehead thing and started making babies, and by the time officials drained the pond two years later there were seven adults and more than 1,000 juveniles. Snakeheads, said Early, had become the dominant fish in the pond, outnumbering bass, crappies and bluegills.

"In the Potomac, we have an outstanding largemouth bass fishery with significant economic impact," he said. "I think we should be concerned about this fish because of the potential effect on species in the river that we are used to and enjoy."

But Early admits snakehead hysteria may be out of proportion. In Asia, northern snakeheads are considered a delicacy. What's wrong with adding a little diversity to the river, I asked, especially if it involves something you can catch and take home and eat?

Early laughed and said that in Japan, where largemouth bass are being introduced in some waterways, people are worried that they will adversely affect the snakehead population.

In any event, he was willing to debunk a few myths about northern snakeheads. They look more like fish than snakes, he said, generally grow to a maximum size of about 30 inches and have regular fish teeth like a great northern pike. There's no evidence they will attack humans, except perhaps to protect their spawning nests. They do not walk on land but can wriggle around a bit, and they can live a few hours out of water, as can eels, crabs, bull minnows, catfish and a few other species. They do not tolerate salt or brackish water.

Snakeheads are particularly well adapted to water where oxygen is scarce because they are able to breathe air. That might come in handy in places like the Potomac, where dead zones with no oxygen grow larger annually as humans dump more and more oxygen-eating nutrients into the rivers and streams.

Early says while he's concerned about reigning in any threat from snakeheads in the Potomac, he's more concerned about other introduced species that do real, immediate damage to the environment, like nutria eating up tidal marshes on the Eastern Shore and mute swans uprooting vegetation.

I mentioned another species his agency might want to focus on that's doing heinous things to all of earth's most vital resources -- land, water and air.

Man.

Contrary to popular belief, snakeheads, above, have teeth akin to great northern pike. Like cicadas, below, they are a bit eye-popping but not harmful to trees.