The trout streams are quiet these days, but fly fisherman aren't. They are tieing flies or learning how to tie flies, because in trout fishing there are two seasons - one for fishing with flies and the other for making them.

Fly tieing is not the pursuit of bug-loving bondage freaks. Fly tieing and its corollary, fly fishing, are the rare sports that can be dignifed by the label "art." Their history traces to ancient Greece and probably goes much earlier, to some wise old fisherman who, lacking bait, wound fur and feather on a hook and fooled a fish.

"Fly fishing is becoming increasingly popular in the Washington area," said Barry Serviente, owner of Angler's Art in Georgetown. "To take fur, feathers and steel and spin it all into something that looks and behaves as if it were alive, so that it will fool a fish, is quite an art."

Some folks ask, "Why not just catch a fly and put it on a hook?" Most aquatic insects are frail; try putting one on a hook and you have nothing but some goop on your fingers.

Serviente's shop offers classes in fly tieing and has assembled a winter program of nationally recognized artists and fisherman. OTher classes in the Washington area are currently being offered by the D.C. and Fairfax County recreation departments.

The first lesson a beginner learns is that flies, generally, are made of methodically wound fur, father and thread. Most are delicate, hand-made creations that imitate the aquatic insects and other tasty morsels that make up a trout's diet. Occasionally tinsel, wire or rubber are used.

"Flies just look complex," said Poul Jorgensen, a nationally recognized professional tier who has been teaching at Angler's Art. "People marvel at how lifelike some flies are. The art of tying them appears mysterious. But every fly has its pattern, and if the tier follows the steps of the pattern he can, with a small amount of dexterity, create something that will catch trout."

Jorgensen added that there is more to fly fishing than the fly. Trout are wary creatures that inhabit the pure cold pools and runs of mountain streams.

"First you have to find the fish. Then you have to figure out what he's eating. Then you have to be able to imitate his food. If you can do all that without scaring the fish, you then have to be able to cast your fly to him and make it look and behave like the real bug."

The second lesson in tieing is that every pattern has a variation. Tieing flies that catch fish is simple enough, but tieing flies to catch more fish, bigger and wiser fish, is an unending pursuit. It is in the pursuit of more effective patterns and variations that fly tieing becomes more complex. All sorts of other skills get into the act.

As a tier progresses, he learns more about the insects he is trying to imitate. He soon becomes an amateur entomologist, studying the lives and behaviour of creatures that inhabit favorite streams. Eventually he develops his own style of tieing, his own patterns and variations that are appropriate to the waters he fishes.

"I know of one tier who watches insects hatch under a microscope; almost an invasion of their privacy, considering the whole purpose of it is sport," said Tom Baltz, a professional tier from the Yellow Breeches Fly Shoppe in Boiling Springs, Pa.

"Some of the top international tiers . . . gained their expertise by fitting aquariums with mirrors so that aquatic insects could be observed from under water - the fish's point of view - rather than from above the water where the angler stands. It is an incredible way to catch fish - a whole world apart from putting meat on a hook."

A visit to Angler's Art of the Yellow Breeches Fly Shoppe reveals a dazzling array of exotic furs and feathers. There are the feathers of Indian gamecocks, mandarin duck, silver pheasant, peacock, even ostrich. There are the furs of mink, polar bear, possum, red fox, squirel, rabbit, deer, moose, mole and muskrat.

"Each material has unique charactistics that are appropriate for particular uses," said Serviente. "Some materials are stiff and hold their shape. Others undulate in the current like the legs and antennae of an insect or the motion of a minnow. Some furs are translucent, others are opaque. Some float, some sink. The different qualities of each can be used to imitate the different qualities of the insects, crustaceans and minnows trout feed on."

A good fly tier can save a lot of money. A top quality, professionally tied fly now costs almost a dollar; the angler who fishes frequently loses a lot of flies. They get snagged in the trees, hooked on the stream bottom or left in fish. If you're lucky they get chewed on by a few fish and just wear out.

Most materials cost only a few cents per fly. The savings can be tremendous.