Pale Morning Dun Overview

• Family:  Mayfly
• Size: 7-9mm, 5-7mm (Size 14, 18)
• Emergence: Late June through late July
• Emergence Time:  11:00 AM – 3:00 PM

The Pale Morning Duns, or PMD’s, are Missoula’s premier summer mayfly hatch. Coming off from late June through late July, the Pale Morning Dun Hatch in Montana bring big fish to the surface with its intensity and consistency.

The Pale Morning Dun are two distinct species of mayfly, (Ephemerella Inermis and E. Infrequens for those who care) Infrequens is a size 14, while the Inermis is a size 18. The same patterns work for both, just sized differently. When you get on a pod of fish, check the PMD size, or just go double dry and let the fish decide! When this hatch is on, it is ON like Donkey Kong! Fish will rise steadily for 2 hours to this blanket hatch, moving from one stage of insect to the next as the prevalent stages change.

Fly Fishing The Pale Morning Dun

It’s wise to have a wide selection of PMD’s, including adults, cripples and emerges. With so many flies on the water, trout will focus on one stage to the exclusion of all others. Make sure your fly selection is wide, so you can match the stage the trout are focused on. If your fly selection is less varied, you might want to move from rise to rise, to locate a fish that’s feeding on the stage of insect you’re presenting. The PMD’s are a great example of needing to buy flies wide and shallow, not deep and focused. 

The PMD nymph has a very slow emergence. After reaching the surface, their thorax slowly splits as the wings emerge. The trout will often focus heavily on this stage, so a floating nymph is an excellent idea when the trout are breaking the surface, but not taking a fly from the surface. It pays to watch the rise form carefully. If only the trout’s back is breaking the surface, they’re feeding sub-surface. But if the nose is coming out of the water, then the fish is eating off the surface. Pay attention to the rise form, so you’re not floating an adult over a fish eating emerges. In contrast to the slow emergence, once the PMD has reached the surface, its wings dry very rapidly in the July heat, and they leave the surface rapidly. 

Missoula Pale Morning Duns

Found in strong numbers on the Blackfoot River, Rock Creek, the Bitterroot River, Clark Fork River around Missoula and many other streams across Montana, this mayfly provides steadily rising fish in between trout slashing for the waning Salmon flies and surging Golden Stones.

When the PMD’s come off, it can be epic. Which brings to mind the concept of a cloud day. Skiers are very familiar with the concept of a powder day. The snow falls, and the skier calls work and says’ “I have a tummy ache”, and heads off to the slopes to ski mid-week on the best snow! The fly fishing version is a cloud day. If you wake up on a July day with strong cloud cover, call your job! Fish love cloudy days- they feel more comfortable for a variety of reasons. Additionally, the mayflies will hatch more strongly in the clouds. Combined, this means the already strong PMD hatch will be amazing. We would love to offer a letter on Missoulian Angler letterhead excusing you from work, but we’re sure management will nix that idea! So you’re on your own for missing work, but we can tell you a cloudy day in July is a treasure- don’t waste it!

Additional Pale Morning Dun Resources