Dark Cahill
The Dark Cahill is a classic Catskill-style dry fly that imitates darker mayflies like Stenonema and Leucrocuta, making it a staple for searches like classic Catskill dry fly, Dark Cahill mayfly pattern, and best darker mayfly dry fly for trout.
Imitates: Adult Stenonema and other dark-bodied mayflies
Quick Reference
- Best Sizes
- #12-16
- Best Season
- Late spring through summer
- Best Conditions
- Evening hatches, freestone rivers, slower runs and tailouts
- Water Temp
- 55-68°F
- Recommended Tippet
- 5X
How to Rig It
Single dry fly during darker mayfly emergences and spinner falls.
How to Present It
Dead-drift along feeding lanes; cast slightly upstream of rising fish.
Why It Works
Its dark, woody silhouette matches many evening mayflies that lighter Cahills miss.
History
A Catskill classic developed alongside the Light Cahill in the late 1800s and refined by Theodore Gordon's contemporaries.
Pro Tip
If trout refuse a Light Cahill in low light, switch to a Dark Cahill one size smaller — the silhouette often wins.
Frequently Asked Questions
What's the difference between Light and Dark Cahill?+
Light Cahill imitates cream-colored mayflies; Dark Cahill matches darker brown and slate species, often hatching later in the day.
Not sure if Dark Cahill is right today?
Get a fly recommendation based on live water temp, flow, sky, and time of day for any river in the US.
Open Fly Advisor
Map
Fly Guide