Dry fly
Iron Blue Dun
Small dark upwing for cold-weather hatches
Trout · GraylingSurface
A small, dark slate-blue-winged upwing dry for cold, blustery days on Irish and British rivers — the iron blue hatches when little else will, often in the worst weather of the early and late season. Dark mole-fur or claret-tinted body, pale blue-dun hackle, upright wings.
Fish this when
Cold, blustery days in April-May and September when Large Dark Olives have mostly finished but a small, very dark dun keeps coming off regardless of the weather. Trout often key onto it selectively because so little else is hatching.
Why it works
The iron blue is one of the few upwings that hatches reliably in cold, windy conditions when trout have few other naturals to choose from — matching it precisely on a bad-weather day beats any general searching pattern.
Naturals it imitates
iron blue dun (Baetis muticus / Nigrobaetis niger)
Typical zone & fishable range
usually
Surface
Film
Subsurface
Deep
Setup sensitivity: medium
Quick facts
Tying difficulty
Beginner-friendly
Heritage
ModernClassicHeritage
Classic
· Ireland/England, traditional — a long-standing early/late-season chalk-stream and freestone pattern