A good thing about Inauguration Day was that federal workers were off, which meant the Endangered Species office at Interior was closed and Jay Sheppard could go trout fishing.

Another good thing was that it was unseasonably warm, which meant little midges and even a few big stone flies were hatching on a Pennsylvania limestone stream called the Yellow Breeches. The midges and the trout and Sheppard had a date.

If finding a hatch and surface-feeding trout in the dead of winter in the Pennsylvania latitudes seems too good to be true, for years it was.

"It was overlooked until the last five years or so," said Tom Baltz, the tall, angular fly-fishing specialist at Yellow Breeches Fly Shop in Boiling Springs. "The midges have always hatched in the winter on the limestone streams, but people used to call them no-see-ums. There were no hooks small enough to tie flies to match them, so nobody fished the hatch."

"Just how big are the midge dry flies we'll be using?" I asked Sheppard as he piloted his rusty van over the rolling hills of south-central Pennsylvania.

"Speck of dust," he said.

So how does a person who claims no great skill with a fly rod fish a fly he can barely see on a stream he's never tried? Badly, in a word.

"The midges are coming off right now," Baltz said when Sheppard stopped in at the fly shop for a last-minute final report. "It ought to be good through the middle of the day."

He sold Sheppard, who had not had time to tie fresh flies the night before, three dry midges and three pupae, all in sizes 24 and 26. The hooks on which these flies are tied are so small it's hard to think of anything to compare them to. If you dropped all six on a rug you'd need a magnifying glass to find them.

The hostages were still in Tehran and Ronald Reagan had not yet taken the oath of office when we pulled on our formal attire of chest waders, fly vests and floppy hats and made our way from the parking lot at Allenberry summer theater to the shallow flats of the Yellow Breeches.

Even in the coldest days of winter this stream and others like it in Pennsylvania's lower tier do not freeze because they are fed by underground limestone springs. The water temperature never dips below 50 degrees and it retains a basic pH factor, making it ideal for trout, which can't abide acid..

There are days when the banks are a foot deep in snow, yet steam is rising off the streams. The streams are an oasis in a frozen wasteland. Even with the air temperature below freezing, as it usually is, some insect hatching occurs as long as there is no raging storm. And the trout feed on the insects.

We saw it right away. Sheppard approached the banks warily, fearful of spooking the trout. He peered over a stone wall. "There," he said. "See that. There's a trout feeding. There's another one."

The trout rose from their resting places in the two-foot-deep water, sipped in floating insects or pupae and descended again to the rocky bottom, leaving behind ripples in the water. It was a sight for winter-weary eyes.

But the capitalizing on it was another matter. The stretch of the Yellow Breeches we were fishing is one of the state's fish-for-fun areas, where only fly fishing is permitted and only one trophy fish a day may be kept. The trophy fish are rarely caught.

Even run-of-the-mill fish are a mighty challenge, because since no other waters are open all the best trout fishermen come here. "These are educated fish," said Sheppard.

Educated by cruel people like the guy in the riffle next door. While Sheppard and I flailed futilely at the water, drifting our tiny dry flies along the surface and watching the wise old trout slurping up bugs on either side, the guy in the riffle next door was catching fish and releasing them.

I finally couldn't take it any more and went over for a closer look. Most trout fishermen, when they see competition coming, cup whatever fly they're using in a hand and refuse to fish until the interloper leaves.

But this fellow had a heart.

"Hatch coming off," he said. "Midges, about size 20 or 22. If you have anything gray in that size you ought to get'em."

We didn't, so we whiled away the day hurling slightly too small flies at slightly too smart trout. Sheppard caught one brown trout. I did not.

Fishing Pennsylvania's limestone streams is known to be among the most demanding angling exercises in the East. Midge fishing is among the most difficult methods for catching trout because the hooks are so small that it's hard to connect, even on a good strike.

But a hatch in January is such a treat it's worth it, regardless of the frustration quotient.

According to Baltz, who is extremely knowledgable about such things, the fly-fishing stretches of the Yellow Breeches at Boiling Springs, Falling Springs near Chambersburg and Big Springs near Newville all have midge hatches in the winter.

Some insects are hatching almost any day, but the milder it is, the better the chances. Wind and cold are the enemy.