By Doug Hoopes

One of the secrets of being a good fly fisherman is to be able to identify the many different insects that are found in and around the rivers, streams, ponds, and lakes you are going to fish.

To do this you must be an amateur entomologist. Now don't panic, it really isn't all that hard. In fact it is quite interesting and can make a big difference in how good of a fly fisherman you can become.

Let's really keep it simple. First of all let's forget those long Latin names that are nearly impossible to pronounce or remember. After all, fish don't know the fancy Latin names anyway. They see an insect that is familiar to them and either eat it or reject it. Sounds too simple? I don't think so. Sure fish have schools, but Entolomology II, forget it.

The only test we will have to worry about is when we use our flies to fool the fish. Remember that it is just as important how you fish the fly, as it is what fly your are using....

We will begin our entomology study with the aquatic insects (an insect that spends most of its life in the water). How's that? Pretty basic.

We should learn to identify both the nymph stage and the adult stage of the stoneflies, mayflies, caddisflies, damselflies and midges. For the time being let's forget about all the rest of the many things that a trout dines on.

Life begins for a stonefly as an egg which hatches into a small nymph, much smaller than a grain of rice. Stoneflies spend from one to three years as a nymph, growing larger each week. Some can get as large as two inches or more before they are ready to crawl up out of the water and begin their adult life. After climbing out of the water they split open the nymph husk and climb out, dry their wings and fly away to the trees and the bushes near by. They mate, deposit their eggs in the water and the cycle starts all over again.

In the nymph state stonefly color will depend on the species and the water that they are living in. The colors can vary greatly, but the most common shades seem to be black, dark brown, light brown, tan and a dirty golden-yellow hue.

The nymphs are easy to identify by the two pairs of wing pads on their thorax (chest), two tails, large antennae, six legs, two claws on each leg and a very fuzzy (hairy) thorax which is part of the breathing-gill system. They require a lot of oxygen and are usually found in the fast part of the stream with a lot of rocks and riffles. Because stoneflies are poor swimmers they climb around and under anything that is on the bottom of the stream bed. They will eat nearly anything that they can find.

When the nymph is ready to emerge as an adult, in preparation for mating, it will move to the edge of the stream and crawl out onto the bank. Darn I am trying to keep this simple but it is getting out of hand.

The mature stonefly has its wings folded flat on the top of its body when at rest. It is not a good flier but moves quickly on its feet, darting around on the ground and in the bushes to avoid being captured. The wings are the clue to identifying the adult stonefly.

Stoneflies have two very short tails and two antennae that are about half the length of their body. They most commonly hatch out in June and July, but are sometimes found earlier and later in the season. Watch the birds flying near the streams. They feed on the flying adults and seem to know when and where the hatch will be coming off. Being such poor fliers, they are easy prey for sea gulls, robins and other native birds.

Mayflies include a large group of aquatic insects. There are several hundred different species in our area alone. This makes it very difficult to simplify, but let's try.

Mayflies start as very small eggs that hatch quickly. The rapidly growing nymphs spend from several months to a year under the water, preparing themselves to make the change into air breathing adults.

When the magic moment arrives, the nymph swims to the surface of the water and floats along on the surface film as it sheds its nymphal skin. It then dries its new wings and flies off to the nearby bushes and trees (At this stage it is known as a DUN). In a few hours it makes another change. Shedding its dun skin, it changes into a sexually mature adult mayfly called a SPINNER. Now it is prepared to mate and lay its eggs over the water to perpetuate the next generation. As it begins its breeding ritual it is again available to the feeding fish.

Sooo .... on the trout's menu we have an egg, a nymph, a mayfly dun and a mayfly spinner. Fish seem to love to feed on all the different stages of the mayfly in its life cycle and this makes it very important to the fly fisherman.

In the nymph stage the mayfly can be as large as one inch long and can vary in color greatly. Usually it is grey, cream pale yellow, tan or olive. The nymph can be identified by its flat-squatty body, one pair of wing pads, two or three tails, very short antennae and hairy gills along the sides and top of the full body.

The sail shaped wings held up-right above the body, the long tails (two or three) at the rear, the short antennae, the slender, tapering segmented body and the six legs make the adult mayfly very easy to identify.

This group of aquatic insects is quite large and can be found in all of our streams, rivers, ponds and lakes. Their life cycle consists of four stages, the egg, the larva, the pupa and the adult. Caddisflies are very easy to distinguish in all stages of their life cycle.

When the larva hatches from the egg it looks like a grub and lives on the bottom. Some species will build a case (elongate cone) of small stones, sand, small sticks or other debris found wherever they live. They are called cased caddis or rock rollers and can be found in many sizes and shapes.

The most common colors of the larva are white, cream, pale-pink, pale-orange, green and olive.

Another species of caddis larva does not build a case but swims or crawls around on or near the bottom as it looks for its food. These are called free living or free roaming caddis.

Still another species builds an underwater web or net that it uses to capture its food much like a spider.

The larva are grub-like with rather smooth bodies and hairy gills (on the lower body and thorax). There are no tails or antennae to speak of and no wing pads. The legs are short and the thorax is darker than the body.

The second stage of development in a caddis life cycle takes place as the larva matures. It seals itself into its case and changes into what is called the pupal stage. When this change is complete the caddis has undergone a complete transformation. It develops very long legs, large wings and long antenna.

After this metamorphosis it climbs out of the case and swims or drifts to the surface where the pupal skin splits open and the completely developed adult flies quickly away. The emerging pupa is one of the most vulnerable stages during the caddis life cycle and is one of the best stages for flyfishers to, imitate.

The adult caddis will live from several days to several weeks. During which time they will mate and return to the water to deposit their eggs either on the surface or by crawling or swimming below the surface to the bottom.

The adult has tent-like wings over its back when at rest which are a little longer than the body. These wings are covered by tiny hairs, are mottled and veined and are moth like. Adult caddis have long antennae and very short tails.

Because there are so many different species of caddis flies (over 800) they hatch throughout the year and are almost always available to feeding fish.

Midges are an important part of the trout's diet. They hatch at nearly all times of the year, and although they are usually quite small, they are very abundant. Fish feed hungrily on the large swarms of emerging pupa on or near the surface of the water. Mosquitos and gnats are usually included in this group of insects.

The eggs and worm-like larva are found mostly in the muck and silt of the bottom in the slower, back-waters near the edge of a stream or in the still water of ponds and lakes. Some of the larva, such as mosquitoes, move around in the stagnant waters as they mature.

As the larva prepare to make their final changes from the pupa to adult stage, they move to the surface of the water, struggle through the film, shed their pupal skin, dry their wings and then fly away to mate. After mating they return to the water to lay their eggs so the cycle can begin again.

Midges are fished with the best results on, or just under the surface film of the water. This is where the fish will be looking for an easy meal.

The Green, Provo and Colorado rivers, and many other streams, rivers and lakes in the west have an abundance of scuds (often erroneously called fresh-water shrimp and other water bugs or beetles). Whenever they are available to the trout they are a major part of their diet.

Scuds are scavengers and are common wherever there is good growth of aquatic vegetation. They are good swimmers and will dart about when disturbed. The size and color will vary depending on their maturity. The most used colors for imitations are a pinkish tan, olive and light gray.

Fish deep and around the under-water weed beds with either a darting motion or simply dead drift the imitation near the bottom.

These insects are found in the slower waters of the streams and in small lakes, such as the ones found in the High Uintas and the Boulder Mountains. Fish them much the same way as you do the scuds.

Insects that spend their life on the land but are available to the trout when they accidentally fall, fly or jump into the water are called terrestrials. This group includes grasshoppers, ants, crickets, worms and beetles. They can be very important to the fly fisherman during the times that any or all are on the water. The locust (cicada) on the Green River can cause some exciting fly fishing.

A few things that you should keep in mind while fly fishing:

a. It is nearly impossible to identify an insect as it flies around or swims past you. Capture it and get a good, close look to determine what it is and its color, size and shape.

b. Do not depend on trial and error when you select the fly you will be fishing with.

c. Learn to read the water and be able to determine what the fish are likely to be feeding on. Then present your fly to the fish in the same way as the natural comes to them.

d. Remember, your goal as a fly fisherman and fly tyer is to successfully deceive the fish and make them believe that the imitation you are using is the natural insect that they are feeding on.

e. The correct combination of color, size and shape, along with a good presentation in the right place at the right time will reward you for your efforts.

f. Becoming a good fly fisherman has very little to do with luck! Your knowledge and skill makes the difference.

g. Each time that you go to the stream or river the insect activity will be different and therefore the fish will be feeding differently. So, don't expect to be successful with a fly that your friend told you was a 'killer' pattern two weeks ago. Sometimes the hatches can change completely in only a few hours.

h. Also, even though a good fly shop really tries to keep up on what is happening everywhere in the area, it is nearly impossible to actually tell you what fly will work.

Take a few minutes before you start fishing to find out what is happening. Then select a fly and present it to the fish in the manner that duplicates the natural insect actions.

Now, get out and enjoy and protect the great fishing we have here in the West.