Billy Westmoreland, the well-known professional bass fisherman, was guest speaker at an anglers' exposition in Arlington a couple of winters ago.

Someone asked him what he would choose if he were allowed only one lure in his tackle box. He had the answer out before the question was finished.

"Plastic worm."

"That's nothing," Glenn Peacock said as he powered his sleek bass boat across the glass-smooth waters of the lower Potomac last week in search of tidewater bass. "Ninety-eight guys out of 100 would tell you exactly the same thing if they knew anything about fishing."

It's worming time again for bass fishermen. That's nothing new, either. It seems like it's always plastic worm time -- spring, summer, fall and winter.

The plastic worm and its close cousins, the grub, the lizard and the hairy jig, are the most devastating bass lures there are. They're all fished the same difficult way, and a lot of times they're the only things that will induce persnickety largemouth bass to get with the program.

Like now, with temperatures dropping and fish on the verge of winter dormancy.

And yet, among the legions of men and women who would rather catch a big bass than sleep or eat, legions still growing after a 20-year explosion in bass-fishing interest, hardly anyone knows how to fish a plastic worm properly. b

"I don't know how many guys have told me they'd give anything to catch just one bass on a plastic worm," said Peacock, who is a professional bass guide working out of Silver Spring.

"Then there's a lot of other guys, like the one I had yesterday, who say when the plastic worms come out they'd just as soon quit fishing. This guy told me, 'If I can't catch 'em on a crankbait or a spinner bait then I'm just not gonna catch 'em.'"

Indeed, there are very few things in fishing any harder than working a plastic worm well. The reasons are simple.

"Concentration," said Peacock, who consistently catches lunkers with worms."Concentration and patience. When I'm fishing a plastic worm, there's only two things on my mind -- watching the line and feeling the worm work across the bottom.

"If I fish a worm all day, when we turn around to go home I won't even remember who my partner is."

Good bass fishermen are perfect studies in one-dimensional living, at least while they're fishing. Peacock put the blinders on at 8 a.m. when he launched his boat at Mallows Bay, a down-at-the-heels little campground near Nanjemoy. He didn't take them off until the sun sank behind leafless trees and pink cirrus clouds and there was no more fishing to do.

He paid no attention to the horde of 30 mallards that scattered in Aquia Creek after we'd cruised two miles across the Potomac to the Virginia side. He ignored the huge flock of mourning doves that erupted from the bank there, too. He didn't bother with the large hawk that hunted prey overhead in Potomac Creek or the great blue herons that squawked off their marshy stands in Mallows Bay.

He watched his line and he felt the worm on the bottom.

He was using a four-inch smoked grub on the assumption that bass wouldn't take a larger six-inch worm this time of year. For eight straight hours, they wouldn't take the smoked grub either. That's where the patience came in.

At 4 p.m., back at Mallows Bay with a day's frustration behind him, Peacock plunked the grub over a half-rotted sunken boat on a sun-warmed bank.

"There he is," he said, jerking back on the rod and grinning as if he'd fully expected the strike on that very cast. "Get the net."

It was a two-pound largemouth and it was rapidly followed by three more, two similar-sized fish and another that barely made 12 inches.

Then the sun set, the wind blew cold and it was time to turn for home.

Peacock is a lot better fisherman than he is a teacher. When he's in hot pursuit of bass, it's hard to get anything more than a mumble out of him. But on the drive home, with a couple of beers under his belt, he let go a few secrets.

The only way to learn to use plastic worms, he said, is to throw away everything else in your tackle box for a year.

"That's how long it takes," he said. He caught his first bass on a plastic worm 10 years ago at age 14 and has been sold on the slippery lures since.

Like any other fishing, bassing requires a certain knowledge of what makes the quarry tick. Peacock believes that when bass get ready to feed, they head to structure -- fallen trees, rocks, pilings or any other solid thing that sticks up from the bottom.

The fish's idea, he said, is to form a wall against which to pin its prey. "He'd never catch a minnow in the open water, but when he can force him against something, he's got him."

The worm, then, should be cast beyond structure of that sort and then dragged back across it. When the worm hits the wood or rock, Peacock eases it up over the obstacle and then lets it drop back down.

"That's when they usually hit -- on the drop."

In order to weave the worm through such obstacles, it should be rigged Texas-style.

That means the hook is threaded through the top of the worm, then out the side and then the point is sunk into the body below, taking care that the worm hangs straight. A bullet sinker of about three-eighths of an ounce is threaded on the line above.

Peacock believes each worm has its season. He favors lizards in the spring, when the bass are on the spawning beds; six-inch worms in the heat of summer and four-inch grub type worms in the fall. All of them get liberal applications of "worm oil" every five minutes to keep them shiny.

In the winter, he fishes black hairy jigs of a quarter to three-eighths of an ounce, with a black, four-inch split-tail pork rind attached to the hook. This is not a worm, of course, but it is fished in exactly the same fashion.

Most bass fishermen are putting their boats up now, but Peacock, a diehard, is convinced that excellent tidewater fishing still lies ahead. The Potomac feeders are getting cold, he said, but shallow rivers on the Eastern Shore of Maryland remain warm and respond quickly to sunny winter days.

The Nanticoke River and Broad Creek, which lie between Seaford, Del., and Sharptown, Md., on the Eastern Shore, are "hot as a firecracker right now," he said, and fishing should continue to be good there well into December.

On Tuesday, Peacock fished the Nanticoke and caught seven bass, the biggest four pounds, a half dozen large pickerel and a mess of perch and crappies.

That's a great day any time of year.