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Isonychia Dun
A dry fly, tied #10–14, a summer pattern. It is tied against 1 named insect in this book — June–September.
Slate wing over a mahogany body, this is a parachute dry tied on a standard dry-fly hook in sizes 10–14 with claret 8/0 thread. Dark dun hackle fibres make the tail, the body is mahogany or claret dubbing, the wing post is white calf so the fly can be tracked, and the hackle is dark dun wound around that post. It is tied against the Isonychia, or Slate Drake, Isonychia bicolor, a mayfly that runs from June through September in water between 55 and 70 degrees. Trout are the fish it is meant for. Because Isonychia emerge sporadically over months rather than in a concentrated burst, the fly does as much work searching likely water as it does matching a hatch, and it is fished on summer evenings over broken current where a visible post earns its keep. It trickles off all summer and into September, which is how long the fly stays useful.
- #10–14Hook size
- dry flyType
- SummerSeason
- 1Hatch matched
What it looks like
A drawing, not a photograph, and not traced from one. Its proportions were read off 5 independent reference photographs of the pattern and written down as 5 measured characteristics — wing angle, tail length against the shank, how far a hackle fibre reaches — every one of which had to hold across more than one of them before it could be drawn. What survives across many photographs of a fly is the fly.
What it imitates
Each of these is the same hatch record the app's own panel reads, so a pattern recommended on a river card in the app is recommended for one of the insects below.
Tying recipe
In tying order. This dressing is the standard one — these patterns have been in the publicrecord for decades — and materials substitute freely: the proportions and the silhouette are the pattern, not the brand of dubbing.
| Hook | Standard dry-fly hook, sizes 10–14 |
|---|---|
| Thread | Claret 8/0 |
| Tail | Dark dun hackle fibres |
| Body | Mahogany or claret dubbing |
| Wing post | White calf, parachute |
| Hackle | Dark dun |
When to fish it
Summer evenings on broken water. Isonychia emerge sporadically for months, so this is as much a searching fly as a hatch match.
A summer pattern. The insects it matches are active june–september, in water from 55°F to 70°F.
Target species
- Trout
Rivers it fishes well
Rivers with a page here that sit in the regions where the insects this pattern imitates are recorded. It is a claim about coverage, not a report of a fish caught.
- Au Sable River northern lower Michigan · July mean 72.1°F
- Catawba River the North Carolina mountains · July mean 76.7°F
- Jackson River the Virginia mountains · July mean 66.3°F
- Muskegon River northern lower Michigan · July mean 71.0°F
- Escanaba River the Upper Peninsula · July mean 68.3°F
- Saint Croix River northern Wisconsin · July mean 77.2°F
- Smith River the Virginia mountains · July mean 51.9°F
- Tygart Valley River the Virginia mountains · July mean 74.6°F
- Kalamazoo River southern lower Michigan · July mean 71.3°F
- Aaron Creek the North Carolina mountains · July mean 76.7°F
- Aaron Run the Virginia mountains · July mean 77.1°F
- Aarons Run the Virginia mountains · July mean 74.2°F
Related patterns
Same type of fly, or tied for the same insects.
- Parachute Adams dry fly · #12–20 — Universal mayfly dun imitation. Every angler carries these.
- Rusty Spinner dry fly · #14–20 — Almost every mayfly spinner is rust-coloured. This covers the last hour of light.
- Adams (Catskill) dry fly · #12–20 — The original. Rides higher than the parachute in broken water.
- Adult Cranefly dry fly · #10–16 — Long trailing legs, sparse hackle, skittered rather than drifted. Autumn and spring evenings on the bank side.
- Adult Damsel dry fly · #10–14 — Blue or olive extended body on a foam post. For midsummer afternoons on slow weedy water.