1. Start the thread on the hook behind the eye. Wrap the thread to the middle of the bend of the hook. This will be the tail tie-in position. Adjust the hook in the vise so that the bend of the hook is at an apex.
2. We are going to use Wood Duck for the tail and wingcase, the feather is on the left. Mallard Flank dyed Wood Duck is also commonly used, it is the feather on the right. Note that they both have barring or dark horizontal markings. Wood Duck tends to be a little stiffer than Mallard Flank and Mallard tends to have longer strands.
3. The portion of the Wood Duck Feather that we will take from is in the inner 3/4 of the feather. The tip strands are too short and the basal strands lack in distinct barring.
4. Cut along the quill about 8-10 fibers. Keep the tips even and attach the fibers at the tail tie-in position so that the tailing end is about the same length as the hook gap.
5. Secure the tag end of the fibers along the top of the hook shank up to an eye width behind the eye. Do not trim the tag.
6. Pull the tag end back towards the tail and secure with thread wraps to the position where the thorax will be. This will be just above the point of the hook.
7. Most WD 40’s use Superfine dubbing for the thorax. The original WD 40 used Muskrat dubbing. The dubbing material is the grayish underfur below the guard hairs.
8. Twist some of the muskrat dubbing onto the thread with a clockwise motion. Push the material upwards along the thread as close to the hook shank as possible.
9. Lock the fibers to the hook shank with one wrap. Then, twist the material further to compact the dubbing around the thread. Wrap a thorax that is football shaped.
10. Bring the butt ends of the Wood Duck fibers over the thorax for a wingcase. Take some care to spread the fibers equally over the back. Pull on the tag ends over the eye so that the material is snug against the thorax and secure with a few thread wraps. You can make legs with the remaining but ends by sweeping them back. The original WD 40 did not have legs.
11. Snip off the butt ends of the Wood Duck and secure with some thread wraps. Whip Finish.
The WD-40 pattern was first tied in 1982 for Colorado’s Frying Pan River, by Mark Engler. Mark guides for Duranglers Fly Shop out of Durango, Colorado. The WD-40 imitates the larger midges that get trapped in the shuck for extended periods. It is more a style of midge emerger than a specific pattern.
WD = Wood Duck
Thread and dubbing can be chosen to match the color of any natural, the most popular colors being Olive, Black, Dark Brown, Gray, and Rust. The black coloration is preferred on dark days while the Gray is preferred for bright, sunny days. The WD stands for Lemon “Wood Duck”, of which each pattern uses this material for the tail and wingcase.
Thread Body and Dubbed Thorax
The original WD-40 had an olive thread body and a muskrat thorax. There are some substitutions in which the Lemon Wood Duck wingcase has been replaced by Krystal Flash or Razor Foam but this would really make it something other than a WD, wouldn’t it? Another interesting variation is to substitute the dubbed abdomen with a glass bead or two. You can also easily incorporate legs to the pattern by utilizing the butt ends of the wingcase rather than trimming them flush to the shank. The WD40 is often tied in sizes 18-24 for tailwaters such as the San Juan river, however, within our Sierra Nevada size ranges from 16-20.
Carl Stout
A recent variation is the WD-50 designed by Carl Stout. Carl takes the pupa one step further with a wing that is busting out of it’s shuck to become an emerger. The wing is often a dyed Mallard Flank in Gray, Olive, Wine, or Brown. The tail continues to be tied with Lemon Wood Duck or Mallard dyed Wood Duck and the wingcase is a Pearlescent Flat Tinsel.
Dyed Mallard Flank, Woodduck
After 2021, actual Lemon Wood Duck has been difficult to find and you will need to substitute Dyed Mallard Flank, woodduck. Hopefully, the material will be available once more as the Dyed Mallard flank does not have the distinctive barring that the actual Woodduck possess.