WD-40

Simple Colorado pattern, deadly imitator of midges and small mayflies.

Printed on the 7 of spades

The WD-40 predates the lubricant joke it gets named after; the initials stand for wood duck and dubbing, which is essentially the whole recipe. A wood duck flank tail and wingcase, a thread body and a small dubbed thorax. It takes a minute to tie and it catches fish in water where far more elaborate patterns fail.

Its usefulness comes from ambiguity at a very small size. In #20 it reads equally well as a midge pupa or an emerging baetis, and on a winter tailwater those are most of what a trout is eating. Fish that see hundreds of artificial nymphs a season rarely refuse it.

It is a fly for cold, clear, technical water. On a freestone river in July it is too subtle to be worth fishing; on a tailwater in January it is often the difference between a blank and a good day.

What does a WD-40 imitate?

Emerging midges and small baetis mayflies.

How do you fish a WD-40?

Fish it deep and dead drift as the trailing fly on a two-nymph rig, or in the film during a midge emergence. Fine tippet, long leader, and patience.

When should you fish a WD-40?

Winter and early spring on tailwaters, and during any midge or baetis activity. A default cold-water pattern.

What are the quick tips for fishing it?

• Go smaller than feels reasonable — #20 and #22 are the working sizes.
• Gray, olive and black cover almost everything.
• Best as the second fly behind something heavier.

How is a WD-40 tied?

• Hook: standard nymph, #18-#24
• Thread: gray or olive 8/0
• Tail and wingcase: wood duck flank fibres
• Body: tying thread
• Thorax: fine dubbing to match

Dressings vary by tier and region. Treat this as the common recipe, not the only one.