The Pale Morning Dun mayfly, Ephemerella excrucians, generally a mid-western and western mayfly, is in the same family as our popular eastern Hendricksons (Ephemerella subvaria) and some of the sulphurs (E. invaria). The former rotunda genus of Ephemerella sulphurs has been combined by the entomologists with the invaria genus and they are both recognized as the same bug.
“Recent work by entomologists determined that it (E. excrucians) is actually the same species as the important Western Pale Morning Dun (prev.Ephemerella inermis), and the lake dwelling Sulphur Dun of the Yellowstone area, (prev.Ephemerella lacustris). Since all three are considered variations of the same species, they have been combined into excrucians, being the original name for the type species reported as far back as the Civil War.”
The first and last time I encountered Pale Morning Duns, or PMDs, was in August of 1982 during my first – and last – gotta rectify that! – trip to Montana’s Bighorn River. The Bighorn had just been published in Fly Fisherman magazine in 1981, having been formerly closed as Indian property. When my brother Larry and I went there, it was on the tail-end of a two week trip. At that time the Three Mile Access was not there, and only about a half-dozen guides were working the river. Indeed, when Larry and I fished at thirteen mile, the only angler we saw all day was a float-tuber that drifted down the river around 3:00 PM. We went upriver in the evening, below the afterbay dam, and again, only one other angler cast his line besides us in that entire long stretch below the boat launch. My, my, how times have changed! The Bighorn has since become one of the most heavily fished and crowded rivers in the whole country. And I have some wet fly stories to tell you about that…another time.
On that August 1982 evening on the Bighorn, there was a heavy black caddis hatch, and it was like a blizzard of insects. They got on our clothes, on our faces, in our ears. Trout in the several hundred yard long stretch rose aggressively. There were probably over two hundred rising fish in a hundred yards of river. But not to the caddis. Among the black caddis, we noticed that there was a small, about size #16 mayfly, light olive in color, drifting along on the surface. It was this fly, a much easier mark for the trout than the caddis, that they were feeding on. But we didn’t realize it. That was over thirty years ago, and at the time and place of my fly fishing experience – mt first trip west, we were not prepared for this. Considering there were scores of trout rising, and we took only a handful of trout, I finally tied on a black Wooly Bugger in desperation and a sink-tip and caught a few more really nice trout until we quit for the night. When we walked up to our car we spoke to the man who had been fishing a couple hundred yards above us. He repeatedly had a bend in his rod. It was he who told us about the PMD and that the trout were keyed in on them, not the black caddis. When he found out we were from Pennsylvania, he said, “You could have tied on a #16 Light Cahill and caught these trout.”
I have been tying PMD patterns for over twenty years, both commercially and for custom orders. Here is my most recent, latest version (three days old) of a PMD Comparadun:
Hook: Standard dry fly hook; generally a #16 is used for PMD’s, but my customer requested size #18
Thread: Danville Flymaster 6/0 #61 Light Olive
Wing: Light natural deer hair
Tails: Light Dun Microfibetts, six fibers – split 3/3
Abdomen: Tan Sexi-Floss
Thorax: Light Olive rabbit dubbing
Head: Light olive
1) Start thread on hook, place wing halfway between hook eye and point.
2) When tying Comparaduns, practice tells fly tiers how much deer hair to use on hook sizes, also the texture of the hair is an issue to be considered. The most important aspect when tying Comparaduns is that the wing must be set at maximum thread tension, as AK Best says about 95% of all tying, “…with the thread just below the breaking point.” The wing height equals hook length when using standard dry fly hooks. Clip a section of hair, comb out the underfur, use a hairstacker to even the tips, and set the wing on the hook with seven tight wraps. Then trim the butt ends on an angle. If your wing moves in response to thread tension after being trimmed, you did not tie it in tight enough.
3) Wind thread to hook point, attach tail fibers. Next wind to hook barb, flare the fibers with left thumb and index finger, and divide the fibers 3/3 with a series of two figure-eight wraps (four wraps total).
4) Wind thread to thorax behind wing, attach Sexi-Floss, s-t-r-e-t-c-h the Sexi-Floss and wind thread to tail and back to thorax.
5) Wrap Sexi-Floss over thread underbody. Secure with three wraps, stretch and trim excess.
6) Dub thorax and finish head of fly.
I vow one day to return to the Bighorn or other river with a population of Ephemerella excrucians mayflies, and fish a PMD hatch. I’m prepared now. That’s one benefit of experience. It teaches you to be ready for the next time.