Actually, it can represent either a single insect or a "cluster" of midges. Because of this, it is possible to fish a fly that's slightly larger than the actual hatching insect that it represents.

This is a comfort to flyfishers who remain uneasy about the prospect of fishing small flies.

The Griffith's Gnat is very effective fished right on top of the water when you see trout feeding on the surface. During winter, this is usually on fairly warm sunny days, quite often in the afternoon.

Normally, the insects on the surface film take a few moments to emerge from their husks. On cold blustery, rainy or snowy days, they can take much longer. During emergence, the midges are very vulnerable to trout. This is when "emerger" patterns are extremely effective. A number of flies have been created to imitate emergers, but the Griffith's Gnat is a fine candidate if you use a razor blade and cut off all the hackle on the bottom so it rides flush on the water surface.

The larvae of bottom-dwelling species are impossible to imitate, but many anglers fish flies that suggest free-swimming species. But all of this activity takes place near the bottom of the lake, out of sight of the angler and usually when there are no rising fish or insects in the air.

During winter, when fly-fishing for trout is something of a leap of faith in the first place, not too many anglers have the stoicism to ply the depths when nothing is happening on the water's surface.

Fishing flies that imitate pupae is another matter entirely. On a warm sunny winter afternoon, if you see midges in the air but no fish are rising, it's a pretty good bet that at least some trout are feeding on the ascending pupae. In addition, when it looks like trout are eating insects on the surface, it's not at all uncommon for them to be actually feeding on pupae.

If rising trout won't take your flies on the top, they are probably intercepting pupae a few inches beneath the surface.

Look for dimplings or bulging rises. When this is happening, the best way to catch fish is to suspend a pupa pattern beneath a strike indicator.

Quite a few pupa patterns have been created in recent years, but the Serendipity and Chan's Chironomid Pupa are both excellent in gray, olive and black.

PRESENTATION MAKES A DIFFERENCE
As in all types of fishing, you'll have a better time and take more fish if you use tackle that's appropriate for the fish, the flies and the setting.

For fishing lakes, I like long rods because they let you keep a long backcast off the water more easily. This is especially true if you're fishing from a low-riding float tube or pontoon boat.

Small flies require fine tippets. Also, you will have less trouble breaking off with a soft rod, because its limber tip functions more like a shock absorber than a stiff rod's.