First tied back in 1982 by guide Mark Engler as an emerging-midge imitation for use on Colorado’s Fryingpan River, the WD-40 was an instant hit. Anglers soon found out that it was deadly as a blue-winged olive emerger, as well, and the fly is very popular throughout the mountain West. Fished as a dropper behind a dry fly, the WD-40 works as both a hatch-matcher and a searching pattern. Sometimes, trout simply can’t resist it, even when there’s no hatch on.
You can also fish it as a dropper behind a nymph to great effect. Adding a bead head helps the fly get down quicker, especially in fast water. Tie the pattern in black to imitate Tricos, or in any other color to match midges and mayflies in your local waters.
This video, by Tim Flagler of Tightline Productions, offers clear, step-by-step instructions for tying a WD-40. He mentions that his favorite size is a 20, which is perfect for the tiny autumn olives (much smaller than their spring-hatching counterparts) that will soon be emerging in rivers across the country.
The WD-40 Emerger
Hook: Standard emerger hook (here, a Dia-Riki 125), sizes 16-24.
Thread: Light olive, UTC 70 denier.
Tail and wing case: Dyed mallard flank.
Thorax: Olive dry-fly dubbing.
Adhesive: Head cement.