Stream Entomology

Why is stream entomology important?  The answer to this is very simple if you are a fly fisherman.  The insect life in and around the stream will dictate the fishing, and how good it is.  Knowing what a trout eats, will make you a better fly fisherman.  Studying river and stream entomology helps anglers identify the insects, the stage their in, and choose their flies.  Trout feed based on the patterns and cycles of the insects.  These insects hatch at different times of the day, the year, and temprature.  When these three variables are perfect they create a hatch, temprature being the most important variable of all. 

    A hatch is when the type of insect transforms from one stage to the next.  Most insects lay there eggs on the waters surface.  These eggs than hatch into there first stage, known as nymphs.  These bugs live underwater, and for approximately a year.  When the season and temprature is right, these bugs begin to hatch.  They swim up to the surface, where they shed their nymph shell.  This occurs much like a butterfly coming out of a cacoon.  Once free of there old skin, their wings emerge, and these insects float on the surface and dry their wings.  This stage is known as dun.  This is prime feeding time for trout.  This is when the insects are most vunerable.  They cannot fly away because their wings aren't in flying condition, so they are at the mercy of the trout and the river. 

    Once their wings are dry, these flies flock to trees for a couple of days.  They then become what is known as a spinner.  These spinners then begin to mate in the air.  Once mating is done they lay their eggs on the rivers surface, and natures cycle begins again.  After the eggs are layed the fly falls dead to the surface, and are favorites of hungry trout. 

    Knowing and being able to identify the types of flies you see, is an anglers only advantage.  You can have a thousand perfect floats by a fish, but unless it is what they are feeding on, you will rarely entice a strike.  Spend some time learning the different types of insects that inhabit the rivers you fish.  Generally, when I arrive at the river, I look to see if there is anything flying around.  If there is  nothing, I begin fishing with a nymph, until I see some risers, or bugs in the air.  Once the hatch begins I then match the hatch and put on my dry fly.  There is no better action than during a dry fly hatch. 

    Matching the hatch is very important.  By being able to identify the species of insect, you can then tie on the appropriate fly.  There are many types of insects and flies out there, but there are four general types that live in trout streams.  These are Mayflies, Stoneflies, Caddis, and Midges.  These four types of flies make up a good portion of a trout's diet. 

Mayflies

    The mayfly is easily identified by its wings that stand upright.  These flies come in many different colors from tan, brown, olive, gray, yellow, and a few others.  There bodies generally curve upward, and 2-3 tails that sweep back and up.  Thaey are generally less than 1/2 an inch, but there are species that grow to 1 1/2 inches.  These flies are very fragile, and flutter through the air with ease. 

Pale Morning Dun
Green Drake
Blue Wing Olive
Blue Quill

Stoneflies

    These flies are generally larger than most others.  Their wings lay flat over their back and bodies versus being in the raised position.  They also have two very distinguished tails.  Normally 1/2 to an 1 1/2 inches long in length, these are a hearty meal for trout.  While not the most gaceful fly out there, you will find these flies on trees, brush, rocks, and the ground most often.

Salmonfly
Goldenstone
Yellow Sallies

Caddisflies

    Caddis can be identified buy the single trait that their wings are much longer than their bodies.  They also form a tent shape over the body when they are at rest.  Usually their bodies are less than 1/4 inch in length, and are brown or tan in color.  Known for their eratic flight, and dance like moves over the water, the caddis are a favorite of trout everywhere. 

Midges

    The smallest of the flies that we have talked about.  While commonly mistaken for mosquitos, thes tiny flies do not bite.  Often black with clear wings, you will find these flies at every river, almost year round.  An extremely small fly, but a very important part of a trouts diet.

Terrestrials

Terrestrials are generally the bugs on land that end up in the water. Generally a much bigger bug and favorite of trout, terrestrials are a great food source. More abundant in the late summer and early fall, terrestrials will take most of the year.

Ants
Beetles
Grasshoppers
Dragonflies
Bees
Catepillars