When does the Large Summer Dun hatch?

June–August, typically 13:00–18:00. It starts from about 10°C, peaks around 15°C and tails off by 20°C.

What flies imitate the Large Summer Dun?

Greenwell's Glory, typically on a #12–10 hook.

Spinner stage: 10–15mm. That matches a #12–10 hook.

Mayfly · Aquatic insect

Siphlonurus lacustris

Size

10–15mm

Hook size

#12–10

Hatch window

Season June–AugustPeak time 13:00–18:00

Water temperature

15° peak

10°20°

How fish feed on it

An evening fall in the margins. Uncommon enough that most people fishing a loch have never deliberately matched it.

Flies that imitate this

Greenwell's Glory

Ecology

Rivers & stillwater

Where you'll find this

Common Occasional

Identification

Siphlonurus lacustris is a species of mayfly belonging to the family Siphlonuridae. This species is present in most of Europe.