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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington
This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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This topic is about the Mayfly Genus Ephoron

On certain rivers in late summer the Ephoron mayflies gives new meaning to the words "blizzard-like hatch," because their large white bodies give a true snowstorm appearance to their enveloping swarms. This is the most intense aquatic insect hatch of the year in places, and sometimes the flies are so thick that it's hard to get a trout to find one's imitation among the carpet of real insects on the water.

Ephoron leukon is most important species in the East and Ephoron album in the West. They overlap in the Midwest. These are the only two mayflies of this genus recognized in the United States, but Caucci and Nastasi in Hatches II report inspecting specimens which did not fit the description of either species.
Martinsburg, West Virginia

Posts: 8
BrettB on Sep 17, 2008September 17th, 2008, 5:29 am EDT
There's quite a big white fly hatch on the Potomac at least around Harper's Ferry. Does anyone know a good nymph or emerger pattern for the white fly hatch? I plan to hit it early, prior to duns coming off and know there is a good deal of nymphal movement and drift beforehand. Maybe I'll collect a few tonight to see color / size / behavior. Any thoughts are appreciated.
Brett Billings
long-time tyer and amateur entomologist
Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Sep 21, 2008September 21st, 2008, 11:44 am EDT
Hi Brett,

I favor two-part "wiggle nymphs" for imitating burrowing or swimming nymphs, but here's a basic white fly nymph recipe that can be tied in either a hinged or standard style:

Tails--a few whitish or pale gray fibers (flue fibers, thin herl, or three strands of thread).
Abdomen--dirty white dubbing, ribbed with fine gold wire or pearl Krystal Flash.
Gills--a sparse clump of pale grayish-white flue fibers, tied in at the thorax and extending back over most of the abdomen.
Wingcase--brown poly yarn.
Thorax--pale pinkish-orange dubbing.
Legs--short clumps of webby white hen hackle, tied on either side of thorax.

I would fish this fly with weight on the leader until the appearance of the male duns. (They emerge first.) Once the males appear, time will increasingly be at a premium. You could continue to fish the nymph, twitching it to the surface in front of active fish, or you can switch to an emerger.

A white Usual makes a good emerger. (I like mine with a pinkish-orange thorax.) You could also tie a version of the nymph with a white Comparadun wing instead of the poly wingcase. I often clip my tippet in half and tie on the emerger or a white Bivisible/Skater. The remainder of the tippet (with the nymph attached) is tied to the bend of the dry. This can be deadly until most of the females have emerged. Unfortunately, that time is not very long. When you see the male spinners flying with the dun husks trailing from their tails, the females start emerging, and things go crazy in a hurry.

I think the toughest part of this hatch comes after the females appear. The mating flight becomes frantic, with the swarm flying like driven snow above the surface and fish leaping to intercept them. This is when the white Bivisible or Skater is a useful fly. If that fly was used in the two-fly rig, you only have to clip off the trailer and skate it in the swarm. This tactic is more successful than most during the thick of the mating activity, but it can still be tough fishing at times.

Once the surface is covered with spent flies, the activity often slows down. Perhaps most of the fish are already stuffed to the gills. If you want to continue fishing into the darkness, the remaining risers can be targeted with a dead-drifted dry. You can use a spent pattern, but a Comparadun seems to work just as well, and I find it much easier to see after dark. I like a synthetic version. On a few occasions, I have had success fishing a white wet fly well into the night. This seems to work best before or after the peak period of the hatch.

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