The WD-40 was originally developed by John Engler on the Frying Pan River as an emerging midge pattern, but can be used just about anywhere.  The WD stands for wood duck, which is the material used for the tail and wing-case of this fly.  It is basically simple in design but very effective on tail-waters when the trout are moving up in the water column prior to a hatch.


Tiemco 2488 Sizes 16 -24
8/0 Rusty Brown (or color to match Thorax)
Wood Duck Flank
Thread - color to match insect
Rusty Brown Hare's Ear dubbing (or color to match)
Wood Duck flank pulled over thorax

Tying Instructions

  1. Start the thread close to the eye and wrap towards the bend of the hook.
  2. Tie in about 5 to 7 wood duck flank barbules for the tail. Wrap the thread all the way back towards the head forming the body of the fly with the thread.
  3. Pull the butt ends of the wood duck feathers back over the body so that they are aiming towards the tail. Wrap the thread towards the back leaving enough room for the thorax (about 1/3 of the length of the hook).
  4. Dub the thread for the thorax (or tie in peacock herl) and wrap towards the eye of the hook and tie off.
  5. Pull the wood duck ends over the thorax to form the wing-case and tie off.
  6. Cut off the ends of the wood duck and whip finish the head of the fly.  Add a drop of head cement.
  7. Brush or pick-out the dubbing to simulate legs.  The wood duck ends can also be drawn back and used to simulate legs.


The WD - 40 is used to imitate the Imago stage of a mayfly or baetis nymph. It can also be used as a or midge imitation.  It can be tied in a variety of colors from red, gray, black, olive or rusty brown.  It can also be tied in a flash-back version using pearl mylar or pearl krystal flash for the wing-case.

Fishing Techniques

The WD-40 is best fished in a dead drift under an indicator.  It can also be fished as a dropper off a dry fly.  As a dropper, it can be effective both as an emerger fished in the surface film or as a nymph along the bottom.  Lastly, it can be fished using the Wet Fly Swing going deep or in the surface film.