Fly Fishing Devon: Instruction & Guiding on Dartmoor Rivers

From drowned insect to 'emerger'

This page explores how wet flies have changed over the last 150 years so that they now:
  • work at various levels in the water column: top, middle and bottom
  • mimic gasses trapped beneath the insect's exoskeleton which help it ascend from the bottom before hatching
  • mimic the bulbous thorax which contains the wing buds
  • mimic emergence of the adult or dun from its immature form whilst breaking through the surface film
The sections below describe some important steps in the evolution of the wet fly from early patterns which represent drowned insects to modern patterns which cover each stage in an insect's life-cycle.

The page concludes with some speculations on the reasons why trout take artificial flies. These ideas are drawn from Paul's earlier academic career which involved research into the stimuli involved in controlling sequences of animal behaviour.
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Winged wet flies

  • these old flies are still effective despite the fact that we now know that very few ephemeroptera hatch from nymph to winged adult beneaththe water surface
  • often fished with the 'across and downstream' or 'downstream-swing' technique
  • unclear what they represented (cripples, drowned spinners?) and therefore they fell out of widespread use
  • but modern insights into the egg-laying behaviour of some female caddis (see below) may explain their effectiveness and restore their popularity
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North Country spiders

  • often called 'soft hackled wet flies'
  • may represent emergers, cripples or drowned spinners
  • developed in northern England and southern Scotland (1857-1916)
  • very sparsely dressed - short thin body of silk, one or two turns of hackle
  • fished with short line upstream and a dead-drift, or with a downstream-swing
  • remain an effective style of fly pattern
  • modern revival prompted by Sylvester Neme's book "The Soft Hackled Fly" published in 1975
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Skues unweighted nymphs

  • introduced (1921-1939) by Skues for use on chalk streams - relatively clear and slow-flowing rivers
  • incorporate a distinct dark coloured thorax to represent wing cases
  • unweighted flies fished across and upstream just beneath the surface  with minimal movement  - dead-drift
  • Skues targeted trout showing 'bulging' rises to pre-emergent nymphs prior to a hatch
  • can be difficult to detect the take unless water surface is relatively smooth
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Sawyer's weighted nymphs

  • Skue's method developed further by Frank Sawyer who introduced the weightedPheasant Tail nymph which was dead-drifted and also movedto provoke an 'induced take'
  • method developed for catching trout that are often visible in clear chalkstreams
  • nymph cast upstream of trout so it sinks to trout's level 
  • then rod tip is lifted - the 'induced take' technique
The simplicity of this fly suggests to me that Sawyer may have stumbled upon important stimuli that elicit a trout's feeding response: upward movement and the ratio between thorax and body size and shape
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  • term 'flymph' describes the transitional hatching stage between nymph (or pupa) and dun or adult insect
  • introduced (1941-1979) by Hidy and Leisenring - influenced by Skues, called "the American Skues"
  • fished throughout water column with movement e.g. the 'Leisenring lift'
  • shaggy body materials trap gas bubbles - may mimic gas bubbles trapped beneath exoskeleton of pupa and nymph that facilitate ascent and eclosion
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  • Advances in macro photography enable us to study insect metamorphosis in great detail at each stage of the life cycle

  • Advances in our understanding of animal behaviour reveal that artificial trout flies are probably effective because they incorporate 'trigger' elements found in the natural insect

  • The law of heterogeneous summation could explain how incorporating several 'triggers' into an artificial fly increases its attractiveness to trout. In fact, the law suggests that these artificial flies could be more attractive to trout than the natural insects they are supposed to represent
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Bob Wyatts Deer Hair Emerger

  • Bob Wyatts Deer Hair Emerger is probably the first conscious attempt to design a trout fly based on what ethologists / behavioural ecologists call 'sign stimuli'. According to Wyatt:

"Borrowing the essential features of Fran Better’s Haystack and Usual, Al Caucci’s ComparaDun, and Hans van Klinken’s Klinkhamer Special, the DHE is designed to present a strong prey-image. It incorporates a couple of primary stimuli, or ‘triggers’: a visible wing and a sunk abdomen. While suggesting natural aspects of the insect, these exaggerated features ensure that the fly will be noticed - what behavioral ecologists call a super-normal stimulus."
  • This article explores the application of ethology to the design of trout flies
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Online resources

  • Photographs of aquatic insects(in japanese) - essential viewing to understand the problem of representing nature in fur and feather 
  • Donald Nicolson's siteis a catalog of new and old fly patterns
  • An excellent videoshowing how to tie a North Country spider pattern the Partridge and Yellow
  • Mike Weaver selects a dozen flies for trout on westcountry rivers and lakes
  • Craig Mathews and John Juracek describe the Sparkle Dun
  • Czech nymphs
  • North Country spiders / soft hackled wet flies
  • Flymphs
    • "From nymph to flymph": Allen McGee's articleon history and development of the flymph
    • Tying Allen McGee's flymphs
  • Bob Wyatt's Deer Hair Emerger
  • Jeff Serena's tying of the March Brown
  • Frank Sawyer tyingthe Pheasant Tail nymph. Step-by-step instructions here
  • Oliver Edward's videois a superb lesson in tying Sawyer's Pheasant Tail nymph
  • Rick Hafele's articleon glossosoma caddis 
  • Jeff Morgan's articleon glossosoma caddis
  • Tying and fishing the Sparkle Pupa
  • Allen McGee's articleon egg-laying caddis
  • Martin Joergensen's articleon his Black Funnel