Understanding Trout Flies

hen you're new to fly fishing—and sometimes even when you're not so new—the subject of trout flies can be a confusing one. For instance, the word "entomology" (the scientific study of insects) seems to crop up everywhere you turn. Latin words are bandied about like volleyballs. You might be thinking you need a Ph.D. in biology just to catch a trout or two. Think again.

Learning about trout flies—and the life forms they represent—doesn't have to be complicated. Sure, it can be complicated. And some people really enjoy learning the hard science of it all. But if you want to learn the basics without having to decipher a word of Latin, you've come to the right place.

Ring That Dinner Bell: Characteristics of a Successful Fly
A stream is like a conveyor belt for food. A trout will find a comfortable place to hole up and let his food come to him. A lake, on the other hand, is more like a smorgasbord. A trout cruises around and snaps up whatever looks appealing. As an angler, it's your job to determine the fly du jour, the fly that most closely matches—in size, color and shape—whatever's on the day's menu. When you do this, you'll optimize your chances for success.

Anatomy of a Fly

A fly consists of various materials tied onto—or "dressed" on—the shank of a hook. Common fly-tying materials include furs, feathers, chenille, Mylar, tinsel and colored thread. In trout fishing, there are four main types of flies—dry flies, wet flies, nymphs and streamers—and literally thousands of specific fly patterns.

Fly size directly corresponds to hook size. A size 14 Adams is simply an Adams pattern tied onto a size 14 hook. If you're unfamiliar with hook sizes, just remember this: the higher the number, the smaller the hook. A size 28 hook is tiny, while a size 8 hook is substantially larger.

Dry Flies
Dry flies are unique in that they're the only kind of trout flies that are designed to float on the surface of the water. A traditional dry fly is intended to represent the adult stage of an insect. It's tied onto a light-wire hook and uses its hackle barbs and its tail to support itself on the water. You can greatly improve a dry fly's ability to float by treating it with fly floatant.

Wet Flies
A traditional wet fly replicates an adult insect that has either drowned or is diving down to the bottom of a stream or lake to deposit a load of eggs.

Some wet flies, particularly soft-hackle wets, also do a good job of imitating "emergers"—immature insects that are leaving the bottom and swimming to the surface to hatch out into adults.

Nymphs
Most nymph flies are tied to represent insects in their various immature, underwater stages of development—namely the nymphal, larval and pupal stages, depending on the species of insect. A handful of nymph flies are tied to represent crustaceans such as freshwater snails and shrimp. Keep in mind that trout do most of their feeding—maybe as much as 90%—below the surface. This is why nymph flies work so well!

Streamers
Streamers are larger flies designed to replicate baitfish, leeches, pollywogs and other "meaty" aquatic life forms. Streamers are especially effective on hefty trout. To them, insects are more like potato chips—a nice snack, but not the whole meal. Streamers appeal to a big trout's sizeble appetite.

Bug Primer (With No Latin!)

Ok, are you ready? In plain old English, we're going to cover the basics of 95% of the bugs you're likely to encounter on any given trout-fishing outing.

Caddis

You'll encounter caddis in streams and lakes all over North America. There are close to a thousand different species of these bugs! The caddis life ycle looks like this:

larva

pupa

adult

There are 2 main groups of caddis larvae: "case-building" and "free-swimming." A case-building larva builds a case around itself with small grains of sand and sticks, while a free-swimming larva ranges about the bottom of the stream without a case. Either way, you can often find caddis larvae clinging to rocks. A few weeks before becoming an adult, a caddis larva seals itself in a cocoon, in which it begins changing into a "pupa." When the pupa is fully developed, it gnaws its way out of the cocoon and heads for the surface. Which flies represent these immature caddis best? To imitate the larvae, you can't go wrong with patterns like the Peeking Caddis and the Cased Caddis, as well as the aptly named Caddis Larva. For pupal imitations, it's tough to go wrong with the Soft Hackle Caddis, Zug Bug or Sparkle Pupa.

As the caddis pupa rises to the surface, it sheds its pupal husk, and the adult caddis struggles out. Depending on the species, adult caddisflies can be anywhere from 1/8" to 2" long. Caddisflies have four wings that extend past the body. At rest, these wings are folded tentlike over the body in an inverted V-shape. Caddisflies have two feelers that extend past the body, long legs and no tails. In flight, caddisflies look a lot like moths; up close, however, there's no mistaking the two. Dry flies that do a nice job of replicating the adult caddisfly include the Elk Hair Caddis, Henryville Special and CDC Caddis.

Mayfly

Like caddis, the mayfly is an extremely important trout-water insect. Mayflies go through a metamorphosis that looks like this:

nymph

adult—dun

adult—spinner

Mayfly nymphs are found in both lakes and streams, usually hiding under rocks or vegetation. There are two fly patterns that have universal appeal as mayfly nymph imitations: the Pheasant Tail and the Gold Ribbed Hare's Ear.

Once the nymph fully develops, it swims to the surface and splits its nymphal skin, becoming a winged adult called a "dun." The dun sits in the surface film and waits for its wings to dry so that it can fly to the shore. Floating on the water, the dun looks like a tiny sailboat, with its wings folded up over its back like a sail. (Mayflies are the only trout-stream insects with upright wings.) As soon as it's able, the dun flies to the shore. A short time later, it molts and becomes a "spinner" and is now ready to reproduce. Popular adult mayfly imitations include the Parachute Adams, Pale Morning Dun, March Brown, Ginger Quill and Blue Wing Olive.

Stonefly

Stoneflies require a lot of oxygen to live, so they're almost always found in rocky, turbulent streams and rivers. The life cycle of a stonefly is a simple one:

egg
nymph
adult

Stonefly nymphs are free-swimming insects that have 2 tails and 2 long feelers. Good stonefly nymph patterns include the Montana Stone, the Bitch Creek and the Brown Stonefly. If you're caught without one of these flies, don't hesitate to try the versatile Woolly Bugger.

Once the stonefly nymph matures, it crawls to land and emerges as an adult. The adult stonefly looks like the nymph, except that it has wings. At rest, these wings are folded flat over its back. The biggest stonefly is almost 3" long, and the first time one lands on you, it'll scare you half to death! Not to worry, however—they don't bite or sting. The Kaufmann Stimulator and the Sofa Pillow are two of many effective adult stonefly imitations.

Midge

As the name suggests, midges are tiny insects. They're most prevalent in lakes and slow-moving streams. Midges metamorphose as follows:

egg
larva
pupa
adult

When fishing midge patterns below the surface, fly fishers generally concentrate on the pupal stage, because this is the stage that's most important to trout. Once the larva has matured, it pupates, at which time the pupa begins its slow ascent to the surface in hopes of hatching into an adult. But on the way up, emerging pupae are often ambushed by hungry trout. Popular pupae patterns include the Midge Pupa in various colors, as well as the Brassie and Chironomid Pupa.

If the pupa does make it to the surface, it hatches into an adult midge. Adult midges have 2 wings and no tails. At rest, their wings are swept back at a 45-degree angle like a housefly. The Adams and the Mosquito are two of the most successful adult midge patterns.

Other Important Insects
Dragonfly nymph & Damselfly nymph

In ponds and lakes, trout love to feast on the nymphs of dragonflies and damselflies. Both dragonfly and damselfly nymphs have 6 legs and large, wide-set eyes. Dragonfly nymphs—the larger of the two—can take up to 4 years to mature and reach lengths of up 2". To imitate the dragonfly nymph, tie on a Whit's Dragon, Carey Special, Doc Spratley or Woolly Bugger. The Hare's Ear, Zug Bug and Woolly Worm can all be used to imitate the damselfly nymph.

At times, terrestrials such as grasshoppers, ants, beetles and crickets find themselves in the water, being gulped up by ravenous trout. This is especially true on lakes and rivers that are lined with overhanging brush, and on windy days when these insects are blown into the water. To be prepared for these situations, always carry a few terrestrial patterns. Popular ones include the Fur Ant, Dave's Cricket and Joe's Hopper, just to name a few.

OK, So How Do I Decide Which Fly to Use?

All right, so you've got a basic grasp of the 4 kinds of trout flies—dry flies, wet flies, nymphs and streamers—and you're on your way to understanding the major trout-stream insects and their various life stages. It's all cake from here ...

When you first arrive at your fishing destination, you'll want to do 2 things:

First, Observe the Water
If you see jumping fish, there's a good chance that they're feeding on insects on or above the water's surface. Likewise, dimples on the water indicate surface-feeding fish. Porpoising fish are usually feeding on insects on the surface or in the surface film. Swirling fish are generally feeding on emerging nymphs or pupae beneath the water's surface. The more time you spend on the water, the better you'll become at recognizing these signs.

Next, Observe the Insects
After checking out the water, you'll need to figure out what kinds of insects are around. This is best accomplished by catching an insect and inspecting it carefully (some anglers even carry magnifying glasses with them for this task). Visible insects can be captured in any number of ways. You can dip a small aquarium net into the water and let the current push insects into the net. Or, you can catch a flying bug with your bare hands (easier than it sounds when the bugs are thick).

If no insects are visible, pick up a few underwater rocks and look at the undersides. Nymphs will often be clinging there for dear life. Or hold your aquarium net under the surface and kick up the bottom a little. Anything swimming away will get caught in the mesh. Once the specimen is in hand, give it a good, long look—then find the fly in your fly box that most closely matches it. You're ready to start fishing.

No Bugs? Try Attractor Flies
When fishing an unfamiliar body of water, or when insect activity is minimal to nonexistent, give an attractor fly a try. Whereas many artificial flies are the colors of nature—tan, olive, brown, black—attractor flies employ bright colors to get the attention of fish. These flies don't resemble any single specific food form, but they look "buggy" (and apparently tasty!) to trout. Popular attractors include the Humpy in various colors, and the Royal Wulff.

Learning More About Trout Flies
One of the best ways to learn about good local fly patterns is to join a local fly club. In a year's time, you will likely accrue more information on trout flies (and where to fish them) than you could learn on your own in a decade.

Another great way to learn about flies is to fish with a friend. Two anglers trying to find the right fly on the same water will do it in half the time. Besides, it's just plain old fun to share the outdoors with a friend.

If you are traveling to fish a new area, never underestimate the value of local knowledge. If an old-timer tells you to use Uncle Albert's Old Irish Iron Blue Dun for the local rainbow trout, then by all means find out where you can get your hands on a couple of these flies.

While on the water, don't be afraid to ask another fly fisher for advice—especially if he or is she is doing better than you. Most anglers are willing to help another angler, but only if you ask. Internet chat rooms and bulletin boards, such as REI's Community pages, are also good places to ask about local fly patterns.

Finally, when it comes to fly selection, remember that there are no hard-and-fast rules. If you're not having any luck with one fly, try another. Finding the right fly through experimentation is one of the subtle rewards of fly fishing. Fly selection will vary, depending on location, time of year, etc. Insects emerge at different times and rates across our country. Fly fishing is one of the rare sports that allows lifelong learning and refinement. No two days are the same, and seldom do you make a trip without learning something.