Mayfly · Aquatic insect
Yellow May Dun
Heptagenia sulphurea
Size
8–11mm
Hook size
#14–12
Hatch window
Season May–JulyPeak time 14:00–18:00
Water temperature
13° peak
10°18°
Hatches from 10°C, peaking at 13°C, tailing off by 18°C.How fish feed on it
The yellow spinner falls in the evening and generally does better than the dun ever did — which, given the above, is not a high bar.
Flies that imitate this
Yellow May Dun
Partridge & Yellow
Klinkhåmer Special
Yellow Humpy
Ecology
Where you'll find this
- British IslesPresent
- IberiaPresent
- The AlpsPresent
- ScandinaviaPresent
- Continental EuropePresent
- Atlantic fringePresent
Present throughout