When does the Large Dark Olive hatch?

February–May, typically 11:00–14:00. It starts from about 5°C, peaks around 10°C and tails off by 18°C.

How big is the Large Dark Olive?

Spinner stage: 6–9mm. That matches a #16–14 hook.

Mayfly · Aquatic insect

Large Dark Olive

Q: What flies imitate the Large Dark Olive?

Large Dark Olive Dun, Klinkhåmer Special, CDC Olive Emerger, Waterhen Bloa, Greenwell's Spider, Pardón, CDC Dark Olive, F Fly, typically on a #16–14 hook.

Baetis rhodani

Size

6–9mm

Hook size

#16–14

Hatch window

Season February–MayPeak time 11:00–14:00

Water temperature

10° peak

5°18°

How fish feed on it

Less of an event than the hatch. Females return to lay through the middle of the day rather than at dusk, and the fall is thin and easily missed. Worth a look on the flats below a good hatch, but the dun is the fishing.

Flies that imitate this

Large Dark Olive Dun

Klinkhåmer Special

CDC Olive Emerger

Waterhen Bloa

Greenwell's Spider

Pardón

CDC Dark Olive

F Fly

Ecology

Rivers & stillwaterChalk streamsTolerates poor water

Where you'll find this

British IslesPresent
IberiaPresent
The AlpsPresent
ScandinaviaPresent
Continental EuropePresent
Atlantic fringePresent

Present throughout

About the genus Baetis

Baetis is a genus of mayflies of the family Baetidae, known as the blue-winged olive to anglers. There are at least 150 described species in Baetis . They are distributed worldwide, with the most variety in North America and northern Europe.

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