Entomology Part 1

As a new fly angler, or even intermediate, one of the most intimidating parts of the sport is choosing the right fly.  Sometimes the perfect, most unique, fly is the ticket.  Other times you can fool a fish by tying on a pink attractor pattern and cast it out there.  I personally feel learning how to read water, rigging and fishing techniques are more important than choosing the correct fly.  This is why my Fly Fishing Level One classes have much less emphasis on entomology and much more time is spent on the subjects mentioned above.  In my experience, I’ve got a lot of fish not having a clue what bug to use.

The bugs will come.  When I first started I had several mentors suggest different hatch textbooks.  I opened the first page and felt completely overwhelmed. The book stayed closed on my bookshelf for two years until I had enough knowledge under my belt to open it back up.  SUGGESTION – Get something with pictures!

REMEMBER: Fly Fishing Takes Effort!

It takes patience and an incredible amount of time on the water to understand the many components.  You’re not going to learn it all at once.  Even those who have been fishing for a lifetime are still learning.  This is not a fad diet, it’s a lifestyle. Enjoy the journey.

With recent discussions in the United Women on the Fly closed Facebook group, I felt starting our Education Section with Entomology would be a great place to begin.  This will be one of many blog posts in regards to this subject.  DISCLAIMER: I am by no mean an expert on this subject, nor do I have a degree in entomology.  This information comes from my personal experiences, countless hours being on the water and even more time spent researching, reading and learning from other anglers.

Entomology defined is the study of insects.  At its most basic level, fly fishing entomology is understanding the category of insects and what stage of life the bug is in. Understanding the hatch comes with experience, studious habits, observation and most importantly time on the water. 

Fly Types

In order to choose the correct fly, you must understand the different fly types.  The difference between not catching fish and tight lines is having a solid understanding of the different fly types and when to use them.

  • Dry flies
    • Float
    • Mature Stage of Adult insects
  • Subsurface Flies
    • Sink
    • Any Immature Stage of Aquatic Insects
    • Nymph Fishing “Catch All” Term for Fishing Under Water
  • Streamers
    • Sink
    • Mimicks Bait Fish and Other Large Aquatic Prey
    • Minnows, Leeches, Sculpins

Dry Fly

A dry fly is the mature stage of any species of insects. The fly floats on the surface of the water.  Dry flies can be further broken down into an imitator or attractor.

  • IMITATORS – Imitates or resembles a type of insect that is hatching from the nymph stage to an adult. Less flash, more natural materials.

  • ATTRACTORS – Weak to little resemblance of a type of insect hatching. This fly has been designed to attract the curious, sometimes less educated, trout. Flashier, bright colors, legs, sparkle and synthetic fibers.
PC – Todd Moen Catch Magazine

Often times you will hear the term “Match the Hatch”.  In this case you’ll probably choose a fly that mimics the actual species that the fish are feeding on.  Examples of species you will might imitate are: Caddis, Mayfly, Midge, Stonefly and Terrestrials.  In some cases, the fish are more educated then others and you’ll choose an imitator versus attractor pattern.

A downfall to trout Dry Fly fishing is they only feed on the mature stage or adult flies about 20% of the time.  That means about 80% of the time, fish are feeding under the surface.  Although your odds are less, there’s nothing quite like watching a trout rise from the depth of the water column to eat the fly you presented. This type of fishing will keep you coming back for more!

Fishing Technique – Anglers tend to fish dry flies on a dead drift.  Dead drift is the fly moving at the same speed of the current. This can be obtained by moving the fly line up or down stream, also known as mending.  Occasionally there are times to twitch or skate your dry fly.

Subsurface Flies

Most insects have several stages to become an adult.  A nymph is a ‘catch all’ term for these immature stages of their life taking place under water.  These flies sink and are very productive and are considered freshwater flies.  Again, fish tend to feed subsurface (under water) about 80% of the time.  This significantly increased your odds of being productive with a nymph.

There can be several immature stages of different insect species happening at once. This creates a tremendous food source for fish under water.  Depending on the stage of the insect, nymphs can be found in several water columns at a given time.

Fishing Technique – The most common technique to fish under water is to use an indicator. An indicator allows you to visualize when a fish has taken a nymph. There are several indicator types such as Strike Indicator “bobber”, Airlock, Yarn, Tabs, Colored Monofilament Line, etc.  Like fishing a dry fly, most anglers will fish their nymphs on a dead drift. The indicator will either go under water, stop or head up stream.  Basically, if your indicator does anything different, set the hook.  “All hook sets are free.”  NOTE – There is some lag time from a fish eating the fly to the indicator moving.  The more you fish this technique, the more you will recognize a subtle take and become more successful.

Another subsurface fishing technique is European Nymphing.  This is beyond the basics and we’ll address this technique at a later time.


A streamer mimics a bait fish or other large aquatic prey.  The fly sinks and can be very effective for all types of fish.  A streamer take can be very aggressive and addicting.  The tug afterall is the drug!


Fishing Technique – Streamer fishing can be done with a floating, sink tip or full sink fly line.  The flies are larger and heavier, so a short (2-5’) leader of heavier weight tippet if recommended in order to turn the fly over.

Most often, the streamer is casted out and stripped back in.  Stripping lines means to pull the fly and line back towards the fly rod.  The strip can consist of short or long pulls, with a combination of different speeds and an occasional pause.  Each day might be different, and you’ll have to explore which rhythm of stripping line the fish are attracted to.  The fly is changing profiles and mimicking the movement of a bait fish.

Stay tuned for Entomology Part 2 – Choosing the Right Fly.  We’ll also continue the subjects of fishing techniques and how to fish all three types of these flies we’ve covered.

© 2018 unitedwomenonthefly.com

Comments (11)

Thanks for the info Heather. This is a nice summary. I didn’t realize the 20%/80% split in where fish take their flies. When I’m using a sinking fly like a nymph or scud, I often use a dry fly as the indicator. Maybe it’s my imagination but I feel like this is sneakier and less alarming for fish. I’ll have to try the shorter leader when using streamers. Thanks for the tip.

Anne – thanks for the reply. Looking forward to hearing about your fishing adventures. =)

Thanks for the info – as a new angler I’m interested in anything I can learn – look forward to more – could you recommend a good site or book to learn more on the topic ? The information seems as you said sometimes overwhelming – thanks much

Vickie – Join our closed Facebook group at https://m.facebook.com/groups/unitedwomenonthefly to get get more information and connect with other womens to help discuss questions. Also check out https://howtoflyfish.orvis/video-lessons as well. Cheers!

Thank you for this. As a beginner, this breakdown and descriptions are very helpful. My “bug” books are also on the shelf at the moment. This is a slow but very gratifying process.

This info was fascinating! Thank you so much. I am a brand. Ew bigger. Looking forward to the next one.

Connie – We’ll be writing it soon. Thank you for the comment!

Awesome blog. Looking forward to part2
Thank you for all you do:). I had no idea that you had to shorten your leader for streamers, maybe that’s why I’ve never caught a fish on one 😬

Thanks Heather! Starting on this adventure and I so appreciate your excellent teaching. Still anxiously waiting for my first tight line! But SO happy standing in a river and enjoying the rhythm of the cast!

Hillary Votaw Burkhart

Thanks for Entomology I, Heather. I have been trying to understand and become somewhat familiar with bugs and flies for quite a while. This blog, together with the Entomology Class at the Women’s FF Workshop in Boise is helping to shine a light! Looking forward to more info. Thank you!

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