Isonychias, also known as Slate Drakes, are an important food source for trout in most Eastern freestone streams and rivers. They are one of the few predatory nymphs and remarkably strong swimmers. Although many tiers incorporate a white stripe down the back of their pattern, it's not always present on the real thing.
Here Matt Grobert is going to tie Vinnie's Isonychia Nymph named for Vincent Caffarra who came up with this pattern many years ago. Many tyers incorporate a white stripe, here a stripped quill from a wood duck flank feather, Vinnie does not usually include one.
Matt begins by mashing the barb and securing a size 12 TMC 5262 into his vise. For thread, he likes Danville 6/0 in black. Start your thread leaving about an eye length space behind the hook eye and carry your thread all the way back to half way between the point and the barb.
For the tail, snip three peacock herls from the area below the eye. Tie them in securely to the top of the hook shank. Iso's have fairly short tails, so snip the herl off to make them about a hook gap in length.
For the rib of the fly, UTC copper Ultra Wire in the small size works exceptionally well. Secure it to the hook shank with thread wraps taken all the way back to the base of the tail then advance your thread to about the 2/3's point on the shank.
For dubbing the pattern calls for a custom rabbit fur blend; two parts claret, one part brown and one part black. Create a fairly substantial dubbing noodle on your thread, enough to make a tapered body over 2/3's of the hook shank. Don't be afraid to manipulate the dubbing noodle and move things around to produce the taper. With the body wrapped, wind the copper wire forward in an open spiral to create segmentation. Secure the wire to the shank with some nice tight wraps then helicopter the wire to break it off clean.
For the wing case, snip about a 1/4 of an inch segment from a dark turkey tail feather. Carefully fold the segment over to form two layers of fibers. Secure the butt ends to the shank immediately in front of the dubbing. It's important that this wing case end up directly on top of the shank.
For the thorax of the fly, use the same rabbit fur blend as used on the abdomen. Now here's a cool little trick. Matt will start the dubbing at the front, leaving a small space behind the hook eye. The dubbing effectively creates a small dam so the rest of the noodle won't sneak forward and crowd the eye. Wrap back to completely cover the wing case tie in point and then forward to that space behind the eye.
For the legs, Matt has chosen an olive brown hen back feather. Snip away the tip portion of the feather, leaving two equal length sets of legs. Keeping the sets of legs separated, secure them to the hook shank to produce legs that extend rearward, not quite to the hook point. Once the feather is completely secured, snip the remainder free and clean up any errant fibers. Pull the turkey fibers forward to form the wing case and secure it to the top of the hook shank with a few nice tight wraps. Pull it rearward and take a few more wraps. You can then snip the fibers off nice and close. Take additional wraps to cover up the butt ends and form a nice neat head on the fly.
Finish with a seven or eight turn whip finish and your Isonychia nymph is complete. This pattern is also very effective when weighted with wraps of lead wire secured to the shank of the hook before tying begins