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Insect Life on the River from Larvae to Adult

You might have fumbled as you started your trout fly fishing journey. Probably, you solely relied on fly recommendations from other anglers or went with any you came by.

For you to be effective in trout fly fishing and hit the necessary spots without missing a catch, you need to understand the life stages of various aquatic flies for brown trout.

Best Flies for Brown Trout

Brownies are cold-blooded and likewise for most of what they feed on. When winter sets in and the temperatures further drop, brown trout become inactive.

The insects they feed on too burry themselves in the silts or rock beds. A rise in temperatures comes with more insect activity and so does the brown trout behavior change.


The Metamorphosis of Insects

The life cycle of insects can be categorized into two-complete and incomplete metamorphosis. For incomplete metamorphosis, the eggs hatch, and the juvenile insects resemble tiny adults.

These insects either shed the exoskeleton or molt until they are adults. They don’t undergo the pupae stage and most insects with the incomplete metamorphosis have the nymph and not the larvae stage.

In the first days, they lack wings. However, wing pads will develop followed by wings. The last moly welcomes the mature reproductive system. Damselflies, stoneflies, and mayflies undergo this stage.

Complete metamorphosis is an advanced type of life cycle and there are four stages to it-egg, larvae, pupa, and adult. In entomology, the larvae is the feeding system and the growth stage of insects.

From their appearance, the larvae look different from the adult insects. This stage is characterized by chewing mouthparts. The full maturity of the larvae makes the insect a pupa. During the pupation stage, most of its inner anatomy is rebuilt.

The adult will emerge from the pupa. All insects’ metamorphosis are controlled by hormones secreted by glands in the insects’ head and thorax of the larvae and pupa.


How to Identify the Fly and Its Stage

Basic entomology is necessary for you to reach the pro stage of fly fishing. Here you need to identify the bug and its stage. We will address the major categories of brown trout insects that anglers mimic using fly patterns.

Stoneflies

The adults of stoneflies have 4 long shiny wings that lie flat on their backs when resting. They have a three-phased growth cycle-egg, nymph, and adult.

You will spot them on fast-flowing waters and because of this, they have flat bodies and stronger legs to cling to rocks. You can identify them by looking for 2 stubby tails and long antennae. These don’t have gills in the abdomen.

Nymphs upon maturity crawl to the shows then emerge. Anglers don’t bother about their emergence stage. After moving to the shores, they are washed into water currents and brownies gather in shallow areas to feed. They mostly hide under the rocks on the sides.

Egg ⟶ Nymph ⟶ Emerald Adult ⟶ Egg Laying Adult


Duns

Let the jargon of fly fishing not confuse you. In angling, a dun is the development stage of a mayfly that is between the nymph and adult stage.

It is scientifically called the subimago phase. It is a vulnerable stage of mayflies because wings develop here but with a dull and opaque color.

Dun’s welcome brownies to feed on the water surface. They are mostly brown-gray or gray with a shade of blue. But you will mostly come across the weird dun patterns in yellow and white-the pale morning dun.

Mayflies for Duns: Eggs ⟶ Nymphs ⟶ Duns ⟶ Adult/Imago/Spent Spinner


Sedges

Sedges are sometimes called caddisflies. Brown trout anglers are interested in the nymph stages of sedges and they will be cased or without cases.

They are a high determinant for the quality of water as they gather where there are clean waters with no pollution.

They don’t survive in poor waters. Sedges are nocturnal and will hide in greenery in the daytime. They mate at dusk on vegetation or flight.

Females lay eggs in or on the water and hatch into larvae in several weeks. The larvae are long and nymphs cylindrical.

Nymphs will either build cases, swim, or make nets. The adults have wings like tents and long antennae.

Egg ⟶ Larvae ⟶Pupa⟶ Emerged Adult ⟶ Egg Laying Adult


Damsel Flies

Damselflies look like dragonflies but the adults of the two have a slight difference in appearance. The damsel adults are smaller with wings held along though parallel to their bodies when resting.

They are also weaker fliers and have separated eyes. The nymphing stage is the longest in the development cycle of damsels.

Their nymphs have thin long bodies with defined wing cases and their color is similar to that of their habitat.

Emerged adults emerge in larger numbers and swim slowly upwards as they pose in between movements until they are on the water surface.

They love to head to the shores and climb on protruding objects to anchor and hatch into adults.

Egg ⟶ Nymph ⟶ Emerged Adult ⟶ Full Adult


Midges, Beetles, Gnats, and Black Flies

Midges are scientifically called Chironomidae. Midges are closely related to mosquitoes and are available on the rivers yearly. They don’t bite despite being mistaken for them.

You must spot them on the brown trout menu. Despite always hunting for larger meals when their prevalence is high, they won’t pass midges if they find any. They hang around and move in huge swarms.

Midges have two long yet narrow wings and no scales. Hardly will you find a midge bigger than size 16. Male midges have longer plumose antennae that look feathery. They have laid-back wings and are different from mayflies.

They grow in four stages and a brown trout angler is concerned about three-larvae, emergers/pupa, and adult/dry. The larvae are tiny worms with segmented bodies.

They are red because of their forage. Its pupa has an air bubble that they emerge from and always make a U shape when under the water surface. Your midge patterns with beaded heads mimic the pupa.

The adults are mostly used for dry fly fishing. They are tiny and quite tricky to fish. When on water, you can mistake them for mosquitoes.

Midges: Egg ⟶ Larvae ⟶ Pupa ⟶ Emerald Adult ⟶ Mating Adult

Beetles like to float lower in the water you can’t spot any high-profile wings.

We all have our own idea of what flies we think should be good to fish for wild brown trout but just because we think it doesn’t mean they will work. Here we will discuss some of the best flies for brown trout and ones you would be wise to carry with you on your next fishing adventure.

I have short-listed seven flies that according to Pat O’Reilly in his book “Matching the Hatch” are called his magnificent seven. These flies when carried will give you an option for almost every situation you will come across when fishing for wild brown trout.  Although we are talking about seven patterns in total we will need several sizes of some patterns to really cover all situations.

Darting and Stonefly Nymphs

Nymphs of pond and lake olives are agile darting creatures and can be found in any depth of water close to the surface, in the middle and at the bottom.  To represent these creatures the gold ribbed hare’s ear has become the angler’s favorite.

Best flies for brown trout - gold ribbed hares ear

The tying pattern is not really that important but more the movement and size of the fly. When trying to get the pattern down deep a lead bodied fly has been developed as well as the gold head both of which are very successful. Letting the fly sink to the bottom then a quick lift of the rod to induce life into the fly will usually bring a take from a cruising trout. Sizes 14 and 16 work well with these.

Check out Best of Fly Reels

Dark Duns and Spinners

Many of the upwinged insects on rivers and stillwaters have a drab olive body as duns and brown as spinners.  A fly pattern that wasBest flies for brown trout - greenwells glory developed in 1854 by cannon Greenwell and James Wright on the Tweed has become the basic pattern for fishing olives during the season.

The Greenwells’s glory as it was named originally tied as a wet fly has now many variations but the dry pattern with starling upwings is probably the best allrounder in sizes 12 and 16.

 

Light Duns and Spinners

Best flies for brown trout - tups_indispensable

A majority of upwinged flies have a pale wing and a fly pattern that was developed in 1900 the Tups Indispensable is a good representation of any light winged flies that may be hatching and a good alternative to the Greenwell’s Glory. Keep in sizes 14 and 16 with you.

Sedges and Alders

Best flies for brown trout - silver sedge

During the summer and autumn months, sedges become very active in the evenings. These hatches are anything from a few millimeters to about 30mm and come in many colors. The most common size is usually around 10mm and a pattern to imitate these hatches and is a good compromise is a silver sedge. This fly pattern has stood the test of time and is particularly good for trout in rivers and streams. I keep sizes 12 and 16 with me for this one.


Damsel Nymphs and Fry

Best flies for brown trout - olive damsel nymph

Damsel nymphs are a staple diet of trout who sit in wait along the shore for hatching nymphs to feast upon in many stillwaters. Many river anglers overlook this pattern when fishing and will usually fish with dry flies or other similar lures. However, a damsel nymph can be very productive and should be carried. A great asset to any fly box is the damsel nymph in sizes 10 and 12 which not only cover trout eating damsels but backs up for trout cruising after fry also.

Beetles, Midges, Gnats and Black Flies

Best flies for brown trout - coch-y-bonddu-dry

Throughout the season there are many tiny black and dark insects from beetles to spiders and flies that get blown into the water from overhanging bushes and trees. So it is essential that you carry something small and dark to offer trout feeding off such insects.

The Welsh name for a small beetle is Coch-y-bonddu and it is this pattern developed for this situation we will use here. Basically, it represents the tiny beetle and will come in handy and can be fished wet or dry in sizes 14 and 16.

Buzzer Pupae

A staple diet for trout on most stillwaters are chironomids and these insects are most desired by trout during the pupae stage when trying to escape the water to hatch into midges. It is at these times when a hatch is on that trout will favor the pupae over most every other insect in the water leaving many anglers frustrated if they are not carrying these buzzer patterns.

Best flies for brown trout - buzzer

A simple suspender buzzer olive in color would be a good one in sizes 14 and 16 to complete our list.

Well, there you have it a selection of seven patterns that any self-respecting wild brown trout angler should carry in his fly box. They have pulled me out on many days when the fishing wasn’t going to plan and I hope they can be successful for you too.

I would be interested to hear what patterns you would think are essential to carry in your box as each location and water type will have its desired flies, but if in doubt try one of these. Also, check out my post on matching the hatch techniques for more information.

 

FAQ’s – Questions about Flies for Brown Trout

What is the Best Fly for Brown Trout?

  • Darting and Stonefly Nymphs – Gold Ribbed Hares Ear
  • Dark Duns and Spinners – Greenwells’s Glory
  • Light Duns and Spinners – Tups Indispensable
  • Sedges and Alders – Silver Sedge
  • Damsel Nymphs and Fry
  • Beetles, Midges, Gnats and Black Flies – Coch-y-bonddu
  • Buzzer Pupae – Suspender Buzzer
  • Streamer – Wolly Bugger
  • Nymphs – Pheasant Tail

What size fly should I use for Brown Trout?

Dry flies 12-16, wet flies 12-16, streamers 4-6 are good. You can get away with others at times but have a selection of sizes and colors in your box to cover more situations.

What colors do Brown Trout like?

The best answer to this is to match the hatch, trout will feed on whatever is hatching so if it’s green then use a green-colored fly.

Is it better to throw my flies upstream or downstream?

Upstream if fishing clear water so the trout can’t see you coming behind and downstream in murky water and using the flow to drift the fly on the swing. If nymphing it’s usually down with a short cast at a 45 degree upwards.

What other Flies do Brown Trout Love?

Pack rabbit strip streamers in size 8, blue, olive, black, or white wooly buggers in size 8, rubber-legged skunks in size 10, pheasant tail nymphs in size 12, beaded and non-beaded green caddis in size 14, and San Juan worms in size 14 and 16.

Which flies should I pack if I want to catch Brownies in early fall and summer?

Mature brown trout are attracted to ants, hoppers, beetles, and other attractor patterns at this time.

Do Brown Trout feed on flies at the bottom of the river?

Brown and other trout sometimes feed on forage at the bottom but they aren’t common bottom feeders. 

When is the Best time to catch Brown Trout?

Feeding time is the best time to catch trout. Target when mosquitoes and other bugs are at their most active. Late evenings and early mornings of warmer days are also good times.

 

Months long fly fishing action with the best flies for brown trout

Aquatic insects live for about eleven months below the water surface. Brown trout will happily feed on larva, nymphs, and pupae throughout the year.

These forms are common and readily catch fish. While you shouldn’t limit yourself to these, understanding the basic entomology of the insects you fish is vital.

It gives an angler an easier time to choose and pack flies depending on the season and location they intend to fish.

Know the stages of these insects to know the best patterns to match with the hatch and which ones to go for when there isn’t any prolific hatch.

Adjusting depending on the water behavior and forage will have a great influence on your fly fishing experience.

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