Overview

Designed by Umpqua signature tyer Mark Engler, the WD-40 has become a staple for tailwater guides across Colorado and the Rocky Mountain West over the past two decades.

It is a simple, sparse fly that suggests life without trying to copy one bug exactly. The slim, tapered body hints at a midge pupa or a small Blue-Winged Olive nymph, and the short tail and wing case suggest an insect that is about to emerge. Trout that eat small bugs all day in clear, slow water tend to inspect flies closely, and a sparse fly that gets the size and shape right is often what they will eat.

How to Fish It

• Behind a heavier nymph: trail it 12 to 18 inches behind a weighted nymph or midge under a small indicator.
• Near the surface: fish it unweighted in the film or a few inches down behind a small dry during a midge or BWO emergence.
• Tippet: 6X or 7X fluorocarbon for sizes 20 to 24.
• Season: midges hatch year-round on tailwaters, and BWOs come off in spring and fall, so this fly earns a spot in the box every month.

Choosing Color and Size

Gray and Black are the classic midge colors. Chocolate is a good match for darker Baetis and other small mayfly nymphs.

Sizes 18 and 20 cover Blue-Winged Olives and larger midges. Go down to 22 and 24 for small midges and highly pressured fish.