When to use it
- During small midge or mayfly activity.
- As a slim tailwater or spring-creek dropper.
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Reviewed technical illustration← Fly Box
Emerger · guide 28
WD-40
Mark Engler's slim Colorado emerger pattern, built around a thread abdomen and barred-fiber tail and wing case.
- Common size
- Often #18–24
- Colors reviewed
- olive, brown, gray, black
- Imitates
- emerging midge, small mayfly nymph or emerger
The standard WD-40 is sparse: a thread body, wood-duck-style tail and wing case, and small dubbed thorax. The CDC-winged WD-40 Plus is a separately labeled variant.
Technical illustration
Identification views
WD-40 reviewed side profile
A schematic profile emphasizing thread abdomen and barred-fiber tail.
- View
- reviewed side profile
- Color shown
- olive thread body and barred-fiber wing case
- Look for
- thread abdomen; barred-fiber tail; barred wing case; small dubbed thorax
On the water
Understand it. Then fish it.
The river, depth, insects, and fish behavior still decide the final presentation. These are reviewed starting points—not a claim about what is happening today.
How to fish it
- Dead-drift at nymph or emerger depth.
- Raise it in the column when fish shift toward the film.
Mistakes to avoid
- Showing the WD-40 Plus as the standard pattern.
- Assuming one universal body color.
Variant control
Small changes matter.
Three reviewed technical illustrations show the identifying profile, construction, and fishing orientation. They are schematic field-guide aids, not photographs.
Reviewed core form
The standard WD-40 is sparse: a thread body, wood-duck-style tail and wing case, and small dubbed thorax. The CDC-winged WD-40 Plus is a separately labeled variant.- Colors shown
- olive, brown, gray, black
- Weighting
- Weighting is identified when it defines the reviewed form; other bead or weight choices remain labeled variants.
Review trail
Sources, rights, and limits.
Pattern facts were reviewed on 2026-07-12. Every image has its own rights record; photographed hand-tied flies may still vary slightly in proportion.