The hatch chart · Mayfly
Iron Blue
Baetis niger
- Natural’s size
- Hook 16–18
- Time of day
- Cold, blustery days
- At its peak
- May
- Fly to try
- Dark CDC F-Fly, size 16–18
The year
- JJanuary: not expected
- FFebruary: not expected
- MMarch: not expected
- AApril: some about
- MMay: main hatch
- JJune: some about
- JJuly: not expected
- AAugust: not expected
- SSeptember: some about
- OOctober: some about
- NNovember: not expected
- DDecember: not expected
In the hand
Small and very dark: 6 mm long with inky blue-black wings and a dark brown-olive body, two tails. Among other olives it looks like a fleck of soot. The male spinner, the “jenny spinner”, has a translucent white body tipped with red-brown.
On the river
Hatches best in the worst weather, in squalls and cold wind when little else is about. Trout often pick the iron blue out of a mixed hatch and ignore larger flies.