Welcome to Not Quite Entomology

Welcome to Not Quite Entomology! This is a different approach to matching the hatch, or learning which insect the fish are really eating. The flies and methods to make it all work will be here as well. We hope this series will inspire you to go out, look on top of and under rocks, check the stream-side vegetation, really investigate your favorite water and learn which are your local trout's favorite foods!


Isonychias - The Mahagony Dun

Old Rupe!
By Old Rupe


This is the Dun Variant, Slate Drake, Leadwing Coachman, and the White Gloved Howdy. If the multi-naming of the same fly doesn't confuse a person, those who really know say Isonychia sadleri and Isonychia harperi are just later broods of Isonychia bicolor. We have noticed for years there was a late June hatch and a August thru October one, but of a smaller size. This is what one would expect of a bivoltine species (two broods a year). The later broods of all multi-brooded species are always smaller as far as I know.

This nymph is classified as a swimmer, it sits on a rock and strains organic matter out of the drift with its front legs. It feeds as a filter feeder and as a predator on other nymphs, diptera, and caddis larvae. It is a tremendous swimmer, able to swim upstream in the faster currents, darting like a minnow. I wonder if smaller Muddler Minnows that are fished with a twitch are sometimes mistaken by nasty old brown trout for the nymph.

This mayfly lives in highly oxygenated moderate-to-fast freestone rivers in the rocky riffles. Other rivers will have a few strays but the majority reside in the fast freestone streams. Some tail-water fisheries, like the Delaware, grow this fly like mid-west farmers grow hogs, a lot of them and all season long.



Now comes the controversy. Almost all the entomologists routinely write that this species doesn't hatch in mid-stream but crawls up on a stream side rock to hatch. The problem is too many of these experts write articles based on what others have written rather than spending time on the stream fishing the hatch. I see so many duns during the hatch in the air and so few shucks on the stream side rocks and weeds. It's hard to reconcile. I have seen them come off mid-stream on a regular basis, and I'm not alone.

Now we know why Ray Drolling's emerger works. His "XT" duns and spinners have always had merit. (See Fly Fisherman magazine's volume 8 [1]:69-77, and Boyle and Whitlock's 1978 The Second Fly Tier's Almanac. Mayflies by Knoop and Cormier, (p-88) quotes Dr. George F. Edmunds, Jr.,". . . that open-water emergence of this nymph is not uncommon." I would say Edmunds spent some time on the stream.

This nymph swims with an up-and-down motion like all mayflies, while stoneflies swim like a fish, which is side to side. This fact should be more than just an amusing aside to the astute fly fisher.

How do we tell the difference between the dun and spinner? It's really easy. Like most spinners the wings are clear, the dun has slate-colored wings. My, it's amazing how many big fish will come up to the spinners that lie spent on the surface, and contrary to the literature how many good fish will attack the emerger/dun.

The nymph has always fished well. It's a 3 tailed, hot dog shaped thing, with gills all over the abdomen. Brownish-black would describe its color. It has a light colored stripe down the top. This stripe is a distinctive characteristic. Tie it in a fat 10-12 size and fish it with a strong twitch. It darts like a minnow. I tie the body with peacock herl and the tail with 3 tapered peacock herl tips. The stripe I represent with a thin strip of silver mylar. A Mustad 9672 hook weighted for the deep runs and un-weighted in the skinny water says it all. A 3-4x long hook is the game.

The emerger/dun is best represented by the XT tie. An inch or so long tie with a 14 hook. The body is an extended deer hair thing covered with either peacock herl or dubbing that represents such. A deer hair wing case or other floater (foam or such in nylon stockings) allows the emerger to float in the correct near vertical position. Other ties are popular, especially in the Adirondiacs. Art Flick's Dun Variant and the parachute tie have their adherents. See the citations for the correct tie on the XT winner, sorry no scanner, or digital camera here. I have seen the nymph/emerger and the total length can be almost two inches long. I've watched it on land, but never had the courage to fish a fly that size. Maybe I can talk Les Young or Rich Colo into trying the long tie. I have to drive several hours to get to the hatch and now really can't until my feet heal.

I tie the spinner with dark turkey biots and an antron wing. The tail is male pheasant center wing barbs that are seen as real brown. I tie 5-6 barbs for the tail. When I remember I tie one wing upright and one wing flat on the waters surface. A 12-14 tie. Caucci and Nastasi's compara-spinner or Wetzel's White-Gloved Howdy in a 8-10 are what a lot of smart fishermen use.

It's a nice event. Big flies when all the rest we see are so small that a microscope is needed to see them. Flies that are 8-14 in the midst of 18-20's. No wonder we love them.

I have tried a greenish egg pattern on an 18 short shank wide gap hook with an 8 inch leader that is tied to the bend of the hook of the spinner. The thinking was that since the spinners on occasion drop their eggs from a foot or more in the air, an egg fall might produce. I have not fished the egg fall well. Try it, maybe I just didn't fish it right.

Those who fish the Delaware are certainly more informed about the hatch than I. There is an old camp song that in part asks what did Della wear. The answer was a new jersey. A more appropriate response might be the slate drake all season long.

The trivia question for the day is why Charles Wetzel called the spinner the White-Gloved Howdy. The answer is that the female spinner looks like it is extending its white hands/feet in a 'howdy' greeting.

Les Young, Ron Koenig, Rich Colo, Ron Kusse among others on this sight are more knowledgeable with regards to this hatch than I am. I just couldn't hint or badger them into writing the article. Ask them in the Chat Room. They fish the hatch all year long, year after year. They know. I'm lucky to drive to the hatch twice a year.

Ask them in the Chat Room here on FAOL. They will let you know when and where. It's sure nice at 11 PM to get a report of what happened on the stream that day.Old Rupe

For the tying method on the one wing up flies, click here.

Special credits: Photographs courtesy of Al Caussi and Bob Nastasi, from their book Hatches II published by Lyons Press.


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