The hatch chart · Mayfly
Yellow May Dun
Heptagenia sulphurea
- Natural’s size
- Hook 14
- Time of day
- Late afternoon and evening
- At its peak
- May, June
- Fly to try
- Pale yellow CDC F-Fly, size 14
The year
- JJanuary: not expected
- FFebruary: not expected
- MMarch: not expected
- AApril: not expected
- MMay: main hatch
- JJune: main hatch
- JJuly: some about
- AAugust: not expected
- SSeptember: not expected
- OOctober: not expected
- NNovember: not expected
- DDecember: not expected
In the hand
No other river fly is this colour: wings and body a clear sulphur yellow, with two tails and, in the dun, blue-black eyes. About 10 mm long. Hatches are a trickle rather than a flush.
On the river
A fly of stony rivers. Because the duns leave the water quickly and come in ones and twos, trout take them less often than their brightness suggests, but the spinner at dusk is eaten freely.