The Book Mailer

Creating the Effective Fly Pattern

excerpted from Sports Afield May 1978

Underwater studies show that a successful fly has a feature that signals “strike.” Here’s how to identify those features and build them into your flies. By Gary LaFontaine

Edward Ringwood Hewitt was the patriarch of the Eastern angling establishment, dogmatic and argumentative by all accounts, but his opinions were based on careful study. In a Trout and Salmon Fisherman for Seventy-Five Years, he wrote, “Personally I shall not be satisfied to fish and not know the laws which govern the subject. I want to know, and I want the fish this enables me to catch.”
During the first half of this century he was the leading innovator in American flyfishing, originator of the Skating Spider, Bivisible and Neversink Stone dry flies. A constant experimenter, he tested the gamut of hackling variations, flat to oversize, achieving results by altering the way the fly indented the surface film. He knew why his dry-fly prototypes fooled trout, creating light patterns on the meniscus to match the actions of observable naturals. Then in his testing he studied the visible response of working fish to the flies.
Hewitt also tried to create subsurface artificials by copying natural nymphs and larvae. He and John Alden Knight originated a series of flat-body nymphs, carefully forming a base for the bodies with plastic wood. The patterns looked correct in shape, size and color, and through the promotions of Hewitt and Knight enjoyed a brief commercial popularity. But the flat-body nymphs, as much as it seemed they should work, were mediocre fish catchers. These flies soon fell into disuse even in the Catskill region.
Hewitt’s dry-fly creations are still sold through catalogs and fly shops, as valuable for fooling trout now as ever. His wet-fly experiments, on the other hand are forgotten. The failure of his flay-body nymphs stands as an example of a flytier’s dilemma: what you see is what you get with a dry fly, but what you see doesn’t matter with a wet fly.
Hewitt is a fair example of the pitfalls awaiting the creative flytier because he know the requirements of any successful pattern. He listed factors governing the attractiveness of a fly in order of relative importance:

  1. The light effects the fly, above and below the surface.
  2. The way the fly is cast and manipulated, including where the fly is placed relative to the fish.
  3. Visibility of the leader to the fish.
  4. The size of the fly.
  5. Design of the fly.
  6. Color of the fly.
  7. Accuracy of imitation of natural insects.

Even by Hewitt’s own criteria, flat-body nymphs were exact imitations satisfying the least important factor on the list. That stress of realistic representations overwhelmed more important factors.
A flytier cannot test his wet-fly creations accurately through trial-and-error casting. Fishing incidents with the patterns are too random: for example, Fisherman A catches six trout with a blue fly and Fisherman B catches two trout with a red fly. Does this prove the blue fly is better? Fisherman A might have a been quicker at detecting strikes, he might have been working different water, or he might have been fishing with a different motion.
A scorekeeper above the river surface has no way of monitoring these angling variable. The only way he could tell if the flies were presented correctly to an equal number of feeding fish would be by actually observing the action underwater.
I began scuba diving in trout rivers because of the frustration of not knowing- just as Hewitt wanted to know- these “laws which govern the subject (of subsurface imitation),” With air tanks on my back and lead buckles on my waist, I began prowling the clear waters of streams and ponds.
Underwater I could nestle just below pods of active fish, learning feeding habits, movement schedules and habitat preferences. As a scorekeeper, I could actually watch trout select or reject artificial flies.
There was something that I couldn’t do, though. I couldn’t list the factors of attractiveness for a fly pattern, not in a pat formula that would apply for creating all subsurface imitations. The hours of observation convinced me that I could neither verify Hewitt’s rules nor formulate a set of my own.
When trout fed selectively, not only on aquatic insects but also on other forms of subsurface life, the visible characteristics of the prey did not equally affect the trout’s process of selection. The motion, light-effect, size or color of the natural were all important, but for different forms different trials proved to be the most important. There was no set list because the formula for a successful imitation varied.
Every prey organism possessed one characteristic that tipped off vulnerability or availability, one that was visible at a greater distance than any of the other traits. When fish fed heavily on a single organism, locking into the stimulus/response pattern, they moved to intercept the prey when they recognized the identifying feature.
This triggering characteristic is always the most important factor in the attractiveness of the natural or, more relevant for the fly fisherman, in the imitation of the natural. If a pattern fails to simulate this main trait, a trout might accept it if the drift hits the fish on the nose. But it won’t move far to pick it up. The fly that doesn’t mimic the triggering characteristic still catches some trout when the feeding is selective, but the effective pattern fools more because it draws fish from a wider area as it passes in the water.
The creation of an effective imitation must be based on an understanding of the habits and appearance of the original in its environment, not on a picture or description of the natural. Because if the organism is alive and dynamic, the new fly pattern, within the limits of the fly tier’s art, must simulate the factors that identify the organism as alive and dynamic.
Each pattern listed below was the result of a separate study. The triggering characteristic, often after long testing and initial failures, was segregated and copied in an imitation. The secondary characteristics, those traits that could still cause a refusal once the trout came closer, were rated in importance and simulated. The flies were then observed underwater in actual tests against conventional patterns, not only the takes and refusals recorded but also the effective attraction distance of the fly. To complete the study, samples of a finished imitation were sent to angling friends all over the country for use on a variety of waters.

LaFontaine Caddis Pupa

When a caddis pupa emerges it fills a transparent sheath around its body with an aire bubble. This globule of air shimmers and sparkles as it reflects sunlight, creating a highly visible triggering characteristic. The sparkle of air, because trout respond so selectively to it, is the key for imitating the emerging pupa.
It was my repeated failures tying to match the caddis pupa that inspired the scuba diving experiments, first to see what the trout saw and second to simulate with a wet pattern that vision. Even the first dive under the surface of the river proved to be a revelation because finally it was possible, if not to immediately recognize the answers, at least to identify the problems.
Silver tinsel, often promoted as the solution for matching the air bubble, appeared very unnatural on any insect imitation underwater. The tinsel flies in tests performed so poorly, worse even than drab wool patterns, that they ranked with Hewitt’s flat-body nymphs as examples of misguided imitation.
Air reflects and tinsel reflects; why shouldn’t tinsel work? Light rays reflected from most shiny surfaces (an air bubble, for example) retain the color of the original light source. If the light is golden yellow of late afternoon or the blue of dusk the rays reflected off the air bubble with be yellow or blue.
Metals, however, are an exception because they reflect selectively. The spectral composition of the original light source is changed to reproduce the surface color of metal. Even if the sunlight is yellow or blue, silver tinsel still reflects silver, copper tinsel still reflects copper-red, gold tinsel still reflects gold.
Although the need was apparent for a different material to simulate the shimmering air of the caddis pupa, in two years of testing I had to reject every natural and synthetic substitute because they looked not more like an air bubble than the wrap of silver tinsel.
Then I discovered a type of yarn that sparkled in the light, a weave mixed with translucent, reflecting filaments. As soon as I soaked a piece of this material in water I knew that it was an answer for imitating the emergent caddis.
This sparkling yarn, a Du Pont synthetic named Tri-lobal, was the basis for a new series of patterns. There were other differences between older imitations and these new flies, but it was this material that was the key to simulating the main trigger characteristic of the pupas, the sparkle of air.

LaFontaine Deep Pupa Caddis Black (genus Chimarra)
Weight: very fine gage lead wire .011
Hook: Mustad-Viking 94840 No. 16-20
Overbody: Black Sparkle yarn
Underbody: dubbed blend of black Sparkle yarn and black fur
Hackle: Black hen hackle (sparse collar)
Head: black marabou fibers
LaFontaine Emergent Pupa Caddis Black (genus Chimarra)
Hook: Mustad-Viking 94840 No. 16-20
Overbody: black Sparkle yarn
Underbody: black fur
Wing: black deer hair
Head: black marabou fibers

Blackfly Larva
The trick of tying a piece of white thread or white horse hair onto the leader as a tippet is one of those ancient techniques proven successful by years of trial-and-error testing. It’s a wonderful little deception for brook trout in headwater streams; wet-fly fishermen snipping the wings on the Black Gnat and tying on the white sewing thread.
Why did this trick work, though? If anyone ever knew the answer, it was lost back in those early wet-fly days of flyfishing. The white thread obviously served as a trigger characteristic, but it was a mystery why it should have any effect on the success of an imitation.
I traveled through the brook trout regions of New England, mostly Maine and upper Vermont, asking questions to ferret out the history of the technique. I talked to fly fishermen who still used the white thread tippet. Mainly, however, I studied those streams where the trick was especially effective.
On on brook in Vermont, where the white thread almost guaranteed good fishing, I put on a snorkel and pushed my face into the riffle. When my eyes adjusted to the light, I recognized strands of white silk billowing in the current. I yanked up rock that was a squirming mass of blackfly larvae.
This insect, so abundant in streams in the spring, pastes a safely line to a rock. If it’s swept away in the flow, the white silken excretions unfurls until the larva hangs taut. The the insect draws in line to regain the hold.
The white thread on a fly advertised that vulnerability of the blackfly larvae. With a new fly pattern that better imitated the secondary characteristics of the natural, and with the knowledge based on an understanding of the insect this “old” trick became a deadly deceit for fooling trout.

Blackfly Larva
(It’s possible to use an 18-inch length of strong sewing thread for a tippet, but it’s difficult to tie this to modern monofilament. It’s easier to tie sections of 5X leader material white, leaving these tied right to the flies.)

Weight: fine gauge lead wire
Hook: Mustad-Viking 94840 No, 16-20
Body: dark olive floss (over entire hook shank)
Thorax: dark gray muskrat fur (palmer wrapped over upper one half of hook shank)
Head: black ostrich herl

Plain Jane
The effects of a triggering characteristic are dependent upon the clarity, swiftness and depth of the water. The right combination of visible traits for a fly under one set of conditions might be wrong in another. Some materials repel as well as attract.
What caused those missed swirls to a Marabou Muddler? It’s a great pattern because the bulky shape of the head, the motion of the marabou feather, and the brightness of the tinsel chenille are all strong attractors. Sometimes, though, the flash of the tinsel chenille, after drawing fish a great distance, spooks them at the last moment.
The Plain Jane, a fly I designed as a drab sister to the Marabou Muddler, retains two of the three attractors, leaving off the tinsel. At moments when it nabs trout that will only swirl around the standard Marabout, it demonstrates a need for balanced subtlety in attraction.

Plain Jane Brown
(also tied in black, gray and green marabou)

Hook: Mustad-Viking 9672 No. 6-12
Tail: brown marabou fibers (thick bunch- a short on-quarter inch extension beyond the bend)
Body: eggshell-white wool yarn
Wing: brown marabou fibers (sparse application – extending only as far as the bend in the hook)
Head: natural gray deer body hair (clipped dense, shaggy and uneven)