bluestreamflyFind water
Menu
Exact source-identified assortment of small beadless WD-40 nymph and emerger flies with slim thread bodies, sparse tails, dark wing cases, and compact thoraxesReal photo · WD-40 assortment from the Farmington River

Emerger · guide 28

WD-40

Mark Engler's sparse beadless emerger: one barred-fiber bunch forms the tail and wing case around a slim thread abdomen and tiny dubbed thorax.

Common size
#16–24 in the reviewed Orvis standard recipe, Orvis demonstrates #20 as a versatile standard example
Common colors
light olive with olive thorax, brown, gray, black, source-photographed thread-color assortment kept individually unlabeled
Imitates
Baetis-type mayfly nymph or emerger, midge larva or pupa, very small sparse aquatic-insect profile
How to recognize it

Look for a curved emerger hook with no bead, a very slim thread abdomen, a short barred mallard- or wood-duck-style tail, the same barred fibers folded over a small dubbed thorax as the wing case, and no separate upright wing. The exact assortment shows color variation but does not establish each hook size or recipe. A two-tailed dubbed RS2 with a short clipped wing, a beaded WD-40, and the CDC-winged WD-40 Plus must remain separately labeled.

Orvis attributes the WD-40 to Colorado tier Mark Engler. The standard reviewed form is the sparse thread-body, barred-fiber, dubbed-thorax fly; the WD-40 Plus adds a CDC wing and is a later, explicitly named variation rather than the page's photographed standard.
Exact source-identified assortment of small beadless WD-40 nymph and emerger flies with slim thread bodies, sparse tails, dark wing cases, and compact thoraxes
Real photo · exact pattern

WD-40 assortment from the Farmington River

One real photograph of a source-identified WD-40 assortment—not multiple viewing angles or a universal color chart. The flies make the beadless slim-body architecture visible; color, hook, size, dubbing, and proportion still vary, and the crop is not a measurement tool.

View
exact pattern assortment — source-identified WD-40 flies
Color shown
olive, gray, brown, and black thread-bodied variations
Look for
One source-labeled assortment shows multiple beadless WD-40s with very slim thread bodies, sparse tails, dark wing cases, and compact dubbed thoraxes in several colors.
Open full-size photo ↗

On the water

Know when and how to fish it.

Use these tips as a starting point. The river, depth, insects, and fish behavior still decide the final presentation.

01

Why it works

  • The thread abdomen keeps the profile exceptionally slim, which fits small midge and Baetis-type food without the bulk of a conventionally dubbed nymph body.
  • One barred fiber bunch supplies both the tail and compact wing case, creating segmentation and contrast with very little material.
  • A tiny darker thorax provides one focal point while the beadless construction lets rig, leader, and current—not a fixed bead—set the fishing depth.
02

When to use it

  • During credible midge or small Baetis activity in tailwaters, spring creeks, lakes, or other clear-water situations where trout are feeding on very small subsurface food.
  • As a slim dropper or point fly when a bulkier nymph is drawing refusals, provided the rig and water-specific multiple-fly rules allow it.
  • Near the bottom for nymphing fish, higher in the column for ascending insects, or near the film only when rise form and observed stage support that change.
03

How to fish it

  • Begin with a drag-controlled dead drift at the depth where fish are feeding; use leader, rig weight, or an appropriate upper fly to place the beadless WD-40 rather than changing its identity with an unlabeled bead.
  • When fish shift upward, shorten depth or use a gentle lift at the end of the drift to suggest ascent without turning the fly into a constantly stripped streamer.
  • Match the smallest visible naturals first by size and body tone, then change olive, brown, gray, or black only when observation or response supports it.
  • Inspect the slim thread body and folded wing case after fish or bottom contact; a loose wing-case tie-down can unravel most of the pattern quickly.
04

Mistakes to avoid

  • Calling a CDC-winged WD-40 Plus, beaded variant, or any slim thread midge the exact standard WD-40.
  • Treating the assortment photograph as multiple angles, assigning a hook size from the cropped coin context, or claiming every photographed thread color is the same recipe.
  • Using the separately named RS2 as another WD-40 image; its split tails, dubbed abdomen, fuller thorax, and clipped wing create a different pattern architecture.
  • Treating the preserved Baetis aureus specimen as proof of the species, size, color, or hatch present on a particular river today.

At the vise

Tie this version.

Standard Light-Olive WD-40 · beginner

This guide follows Orvis's standard light-olive, beadless WD-40. The exact Flickr hero is one source-identified assortment whose individual hook sizes, thread colors, thorax blends, and hidden tying details are not all documented. Brown, gray, black, beaded, and CDC-winged WD-40 Plus forms must remain separately labeled.

Materials

Hook
Standard emerger hook, #16–24; Orvis demonstrates a Dai-Riki 125 in #20
Thread and abdomen
Light-olive UTC 70-denier thread
Tail and wing case
Dyed mallard-flank fibers with fine wood-duck-like barring
Thorax
A very small amount of olive dry-fly dubbing, slightly darker than the thread body
Head
Light-olive tying thread with the hook eye left clear
Adhesive
One controlled drop of head cement on the finished thread wraps

Steps

  1. Start light-olive thread behind the hook eye, leaving enough room to finish a small head.
  2. Cut a narrow segment of barred dyed-mallard fibers, secure it on top of the shank, and keep the bundle centered as thread travels well down the curve.
  3. Set a short sparse tail at the rear while preserving the forward fiber butts that will later become the wing case.
  4. Wind the tying thread forward in smooth touching turns to create the slim tapered abdomen, then flatten and control the forward fiber butts behind the eye.
  5. Dub only a tiny amount of slightly darker olive dubbing onto the thread and build a compact thorax without obscuring the abdomen's narrow profile.
  6. Fold the reserved barred fibers back over the thorax, secure them with two firm wraps, and trim the excess close without cutting the tying thread.
  7. Make a three- or four-turn whip finish, clear the eye, trim the thread, and add a small drop of head cement to protect the wing-case tie-down.

Tying source: WD-40 Fly Pattern & Tying Instructions ↗

Common variations

Small changes can make a different fly.

One verified, non-AI CC BY-SA photograph shows a source-identified assortment of exact beadless WD-40s in several thread colors. It is one photograph—not multiple viewing angles—and the crop does not provide calibrated hook sizes. A finished original-style RS2 is a named-pattern comparison, while a preserved Baetis aureus nymph is a natural-insect anatomy reference; neither is another WD-40 or proof of a current hatch.

Farmington River WD-40 assortment

One exact source-identified group photograph shows several sparse beadless WD-40s with barred tails and wing cases, slim thread bodies, and small thoraxes. It is one assortment image, not several independent angles.
Colors shown
olive, brown, gray and dark thread tones, barred mallard-style fibers
Weighting
No bead or external weight is visible; the photograph does not establish each hook size, hidden ballast, or exact color recipe.

Rim Chung original-style RS2 comparison

A separately named finished RS2 exposes the boundary: two long split tails, a tightly dubbed abdomen, fuller thorax, and a short clipped saddle-hackle-web wing rather than the WD-40's thread body and folded barred-fiber wing case.
Colors shown
natural gray-tan, dark gray, dark dun
Weighting
Named-pattern comparison only; the photographed RS2 is beadless and is not a WD-40 variation.

Natural Baetis aureus nymph reference

A scientific preserved-specimen photograph shows one slim Baetis nymph with a narrow abdomen, three tails, wing pads, legs, and lateral gills for natural-body-plan comparison.
Colors shown
pale olive-tan preserved specimen, dark internal markings
Weighting
Natural insect reference; not an artificial fly, local species claim, exact hook-size guide, or evidence of today's hatch.

Related patterns

RS2 ↗Blue-Winged Olive Patterns ↗Midge Patterns by Stage ↗Zebra Midge ↗

How this guide was checked

Fly information and photo sources.

Guide checked on 2026-07-13. Every image has its own source and usage record. Natural insects and hand-tied flies can vary in shape and proportion.

Pattern sources

Orvis Fly-Fishing Learning CenterWD-40 Fly Pattern & Tying Instructions↗Orvis NewsHow to Tie the WD-40 Plus↗freyfisher / FlickrWD-40's save the day more often than not on the Farmington R. in CT↗Orvis NewsHow to Tie the RS2↗

Image credits