BUGS

In his videotape, Nymphing, Gary Borger quotes a wise man as saying, “It’s best to begin at the beginning.” The beginning for fly fishermen is knowing about what trout eat. So, let’s discuss food organisms.

Many anglers have a casual understanding of Mayflies, Caddisflies, Stoneflies, Midges etc. But that’s as far as it goes. They find the extraordinary number of bugs overwhelming so they fish attractor patterns.

I suggest you familiarize yourself with one stream. Learn its’ biomass and the stream life of other waterways will fall together.

Let’s compare aquatic insects to members of the animal family.

 

Mayflies

Order: (Ephemeroptera)

Dogs. There are big Dogs…

 
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and little dogs…

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There are dogs of all shapes and colors.

They are all dogs but they aren’t the same.

There are big Mayflies like Hexagenia…

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and little Mayflies like Tricorythodes (tricos).

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There are Mayflies of different colors and sizes. They are all Mayflies but they’re not the same.

All dogs have the same life cycle. All Mayflies have the same life cycle.

Mayflies start life as an egg. The egg hatches into the aquatic, immature stage of the insect called a nymph.

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Nymph

When it’s time for the nymphs to become adults, they congregate in the slow water at the bottom of the river (the cushion). At a predictable time, they ascend to the surface where they encounter the surface film (the meniscus). This is a big deal because the emerging insects (emergers)…

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Nymph changing to a dun

have to get through the meniscus while escaping their shuck. They are helpless. The trout pick them off as they struggle. 

Upon escaping the shuck and getting through the film, the insect becomes a dun.

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Dun

Duns are sexually immature adult Mayflies. They ride the surface film until their wings dry, then fly to the foliage where their skin dries. It splits open allowing the sexually mature adult to crawl out of the shuck and is now called a spinner

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Dun changing to spinner.  Photo by Christian Berg

Spinners have the silhouette and size of a dun but they're shiny and translucent

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Baetis spinner

The spinners mate over the water and deposit their eggs.

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They then fall into the surface film and die.

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Wild trout don’t do a lot of chasing. They have the instincts to know if they don’t feed energy efficiently they will die. This is one of the reasons genetically deficient hatchery fish often die within eight weeks of stocking.

At hatch time start fishing with nymph patterns in the cushion.

When you see dimpling rises switch from the nymph pattern to an emerger. A parachute pattern is an emerger imitation. Wild trout prefer emergers to duns because there are more of them and they are easier to catch.

When the dimpling rises change to simple rises change to a dun imitation.

When you see spinners on the water fish a spinner pattern.

We’ve discussed fishing the cushion, nymphs, the underside of the surface film, emergers, on the film, duns, and in the film, spinners.

We don’t spend any time fishing insect imitations between the cushion and the film

Point to remember

Fish the cushion and the film.

Caddis

(Order: Trichoptera)

There are big cats and little cats, white cats, brown cats, black etc. They are all cats…

 
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but they aren’t the same.

Cats have fur like a dog, two ears like a dog, four feet, a nose and the same life cycle. But they aren’t dogs they are cats. There is no such thing as a Cocker Spaniel kitten or a Persian puppy. There is no such thing as a Mayfly pupa or a Caddis nymph.

Caddis are aquatic insects like a Mayfly, but they aren’t Mayflies they’re Caddis.

There are Caddis of all colors and sizes, but all Caddis flies are not the same.

Caddis eggs develop into larvae.

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Larvae are wormlike aquatic versions of the Caddis. Some larva build cases out of sand and stone, some from wood and other aquatic vegetation, some spin webs, others are free living.

Larvae grow the most in the weeks prior to emergence.

 

About three weeks prior to emergence, they seal themselves inside of an immobile pupal chamber and transform to a pupa.

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Photo by Don Douple

Some adults exit their pupal shuck and crawl ashore, (at these times you’ll find fish feeding in very shallow water).  Others form an air bubble for buoyancy and escape their pupal shuck in the film as they ascend rapidly, pop through the meniscus, and take off. This can drive fish nuts!  Many times, when you see fish clear the water, they are chasing these adults. (See Leisenring Lift) This is a time when wet fly fishing and dry fly-fishing merge. You use a pupa pattern but add floatant! I like a product called Frogs Fanny. It floats the fly like a cork and provides wonderful bubbles.

The adults…

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fly to the vegetation, In England they call them sedges because they go to the sedge grass. They feed for a week or so as their eggs mature. The adult’s head to the water, deposit their eggs and die. When there is a preponderance of adult Caddis on the surface, they are usually dying spent adults. (Fish for them with a twitch).

Many folks came into my shop asking for Black Caddis patterns because they see Black Caddis flying over the water. The problem is these bugs were over the water, not on it. I don’t know how to consistently imitate airborne insects. Black Caddis crawl into the water to lay eggs.

Point to remember

Be observant.

Midges

(Family: Chironomidae)

Anglers call diptera of the chironomidae family Midges to distinguish them from other small aquatic insects like Mayflies.

Midges are aquatic insects like Mayflies and Caddis

Midge eggs develop into larva. Larvae are wormlike aquatic versions of the insect.

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Prior to emergence, larvae seal themselves inside of an immobile pupal chamber and transform into a pupa.

Prior to emergence the pupae congregate in the slow water, or cushion at the bottom of the stream. Wild trout also concentrate there because fish can't spend their lives fighting the current. As the concentration of pupae increase, the trout notice them and begin to feed on them.

When it's time for the pupa to "hatch" they ascend...

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Photo by Jim Schollmeyer

from the cushion, to the surface. The trout follow them to the surface and suspend.

Upon reaching the surface, the pupa encounters the surface film (meniscus.) which is difficult to penetrate.

Midge pupa suspend below the meniscus and bore a hole through which they crawl to ride the surface. Surface tension holds the pupal shuck under the film. Trout pick off the vulnerable emerging pupa as they struggle to penetrate the film.

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Photo by Don Douple

Point to remember

Adults on the surface mean there is pupa in the film.

Stoneflies

(Order: Plecoptera)

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Photo by Cathy Mainardi

Horses are animals as are cats and dogs but they aren’t the same.

Stoneflies are aquatic insects as are Mayflies, Caddis and Midges, they aren’t the same.

Stoneflies are usually the largest bug in the stream

They begin their one to three-year life cycle as an egg which hatches into a nymph.

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From http://d-baylor-flyfish-art.com/book-and-dvd-set.html

Stoneflies hatch by crawling out of the water. Their skin dries and the wing case splits open. 

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The adult emerges.

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Photo by Don Douple

Unlike Mayflies and Caddis, adult Stoneflies live for a month. They have the ability to feed.

Point to remember

Stoneflies are most important to the angler when they fall to the meniscus after mating and dropping their eggs from above.

Terrestrials

Terrestrials are land insects that end up in the water and wish they hadn’t.

Consider fishing terrestrials in the wind, or when the water rises.

Terrestrial drift can provide a great deal of food for a fish in a day.

Terrestrial drift is largely a surface phenomenon but it can also trigger subsurface feeding.

Grasshoppers and crickets provide lots of nutrition in areas of high grass. Willow Beetles, Japanese Beetles, Jassids and Inchworms find themselves in the water and become trout food.

I helped Fran Gough with his insect study in the Little Lehigh. Fran put nets in a riffle and checked them every hour on the hour periodically for 4 months. We noticed substantial numbers of ants in the drift during the early morning hours.

I believe ants have a flavor fish relish. Cautious, energy efficiently feeding trout will turn themselves inside out to get an ant. They love them. I don’t think the color is important as long as the silhouette is right. Fish them dead drift on top or bottom, or in tandem.

Point to remember

Ants are one of a trout’s favorite foods.

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