Basic Fly Fishing Entomology

Fly Fishing Entomology is just about knowing what type of insect you are trying to imitate and how to identify their life cycle. Entomology is the study of insect’s in general so we narrow it done to water based insect’s

The most common insect’s we will see on or in the water are listed below and we will take a closer look at each one. If you have an assortment of flies that cover each insect’s life cycle you should do all right, or you could be like some of us and have one of everything available

  • Midge
  • Mayfly
  • Caddis
  • Stonefly
  • Terrestrial
  • Scuds & Sowbugs
  • Annelids (Worms)
  • Damselflies, Dragonflies and Water boatman


Often mistaken for a mosquito midges are found in rivers year round and trout eat them regularly, it is easy to tell if they are midges or mosquitoes by the fact that midges don’t bite. Quite often trout will look for bigger meals but a midge pattern is always a good fly to throw.

The three stages of a midge that fisherman worry about are Larva, Pupa(emerger) and Adult(dry fly). Midge larva are worm like with segmented bodies and are often red in color.

Midge Pupa the difference between the Pupa and the Larva is the pupa has an air bubble and often are seen in a U s


They vary in size and color and are a staple in the trout’s diet. Mayflies have two transparent vertical wings trout feed on them while they dry their wings on top of the water as well as the nymphs as they work their way to the surface. Nymphs are distintive as they have two or three tails and long legs


there are 1400 species in 20 families of Caddisfly in North America. At about the same time each year the larvae begin to pupate, which means the cocoon themselves like a moth and transform into a flying adult. They then chew their way out of the cocoon and swim to the surface. Caddis larvae drift with the current. Adults look like a small moth and with all the different species there will be a number of variations in color and pattern.


Stone flies do to their size are a big part of a trouts diet, they can be found on every continent except Antarctica 3500 verieties. They have a long life cycle from one year for small species to three years for larger species, spending most of that time as a large nymph. They go from Egg to Nymph and then Adult totally missing the normal pupa and dun will know when stoneflies are hatching do to the amount of husks on vegetation by the water. They have two tails and crawl around the bottom of the river. there are four main families of stonefly important to the fisherman they are Salmonfly, large Golden Stone, Yellow Sally and Skwala.


    Terrestrials are Grass Hoppers, Ants and Beetles not a lot to say about this group except there are a large amount of variations and colors. We have hoppers in a number of colors and sizes. Ants are every where in lots of colors and a wide variety of Beetles roam our world. At select times of the year trout go crazy for hoppers and will take ant and beetles most of the time.

    Scuds, Sowbugs and Annelids

    Scuds ( fresh water shrimp) are from five to eighteen millimeters and normally olive grey color. They are found in most fresh water where there is aquatic vegetation.

    Sowbugs usually brown with worm like markings on their backs are similar to scuds with a different body shape, and bigger in size one to two centimeters.

    Annelids are not earthworms or night crawlers but an aquatic worm, smaller and skinnier. They come in a bunch of different colors like red, pink, brown, tan and maroon

    Damselflies, Dragonflies and Water boatman

    Dragonflies are one of the oldest insect’s on the planet with fossils dating back 200 million years. ther are over 450 species of Dragonfly in North America in seven families. The nymph stage is the one that trout mostly go after, it is another bottom of river crawling insect

    Damselflies are closely related to dragonflies and like drgonflies trout mostly eat the nymph stage. Another crawling bottom feeder but with a longer body

    Water boatmen are widespread and common inhabitants of lakes, ponds and slow moving stretches of rivers and streams throughout North America. ther are 525 species worldwide with 130 in North America


          So that gives you an over veiw of what is out there for trout to eat there are a lot of different pattern and colors to use. this can lead to having a lot of flies in your bag but if you stick to the basics and then expand from there you will have luck. A siene net is a good thing to have then you can screen the water and see what is there.

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