When we wrote Fishing Yellowstone Hatches in 1992 we said Epeorus (Ee-pee’-or-us) mayfly emergences were… “sparse compared to other mayflies on the Madison , Gallatin , and Gardner Rivers . Don’t expect to see the water covered with adults and likewise don’t be put off by small numbers either; the sheer size alone of Epeorus is enough to get the trout feeding actively”. In the eleven years since the first printing of this book, Epeorus mayflies have become very important on the Madison ; during both heavy emergences and spinner falls. The mayfly is present on the Madison from late June to well into August.

There are several theories being bounced around to explain the new phenomena. Some entomologists and fisheries biologists feel increased water temperatures during the past several long, hot summers have brought on huge numbers of this mayfly. They point out that Epeorus are warm water insects, and warmer water temperatures are responsible for heavier emergences and subsequent spinner falls. Others feel that since this mayfly is a fast-water species and because the Madison River has run bank full during Epeorus times the past few summers, their numbers have greatly increased. The river has run large in prior July and Augusts creating much more habitat for this mayfly. The increased flow on the Madison is due to fisheries personnel releasing more water from Hebgen Lake during high temperature periods to keep the river cool below Ennis Lake . The lovely mayfly doesn’t seem to care either way. It’s a fact, emergences and spinner falls of Epeorus mayflies occur daily from late June to mid-August and trout feed readily on duns and spinners.

  Epeorus albertae (alber’-tee) is the most important species. The common name, “Pink Lady” is derived from the body color of the female dun and spinner of the species. There is a strong pinkish-orange cast to the bodies of the female duns. The male duns have pale olive bodies and both species have jet black eyes with heart-like markings on their front legs.

This mayfly is interesting because of its unique emergence method. The duns shed their nymphal shuck as they ascend on their way up to the surface to emerge. It seems the trout recognize and accept an emerger whether it is fished on the surface or underneath. The duns usually emerge from 5 to 7p.m. with spinner falls occurring 8 to10p.m. Trout love Epeorus mayflies, at all stages whether it be an emerger, dun, or spinner. Let me share one night of Epeorus fishing this past summer.

August 5 th , at 7p.m . I arrived at $3.00 Bridge; it was rainy, windy, and cold. I considered heading home knowing the evening caddis wouldn’t show due to the weather. In the parking lot I visited with friends who had fished the river during the day and were now heading to dinner. They had a good day on nymphs. I decided to put in some time upstream of the bridge; at a spot we call the “Honey Hole”, as trout always rise here in the evening. I put my three bucks in the safe and headed into a cold rain.

I got to the Honey Hole at 7:30p.m… “the fish were rising everywhere for Epeorus cripples and emergers that were all over the surface. The cool, damp weather with high winds were causing some of the duns to skitter on the surface, some were knocked over and trapped in the surface film. Rainbows were sipping and moving for the emerging duns in the slick below the three rocks that make up the Honey Hole. Brown trout were rising aggressively in their holds near the bank. I caught better than a dozen trout over 16 inches in an hour….fish at first took our Epeorus Emergers and Sparkle Duns. Then just before 9p.m. the wind calmed and all trout switched to an Epeorus Spinner…Easily the best night I’ve had on the river this summer.”

Be prepared from late June through August for this great mayfly activity with emergers, duns, and spinner patterns. Make sure you check out our new Epeorus patterns. They can make a huge difference in your evening fishing success on the Madison River !