When does the Pond Olive hatch?

June–October, typically 11:00–18:00. It starts from about 8°C, peaks around 14°C and tails off by 20°C.

What flies imitate the Pond Olive?

Greenwell's Glory, CDC Olive Emerger, typically on a #16–14 hook.

How big is the Pond Olive?

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

Mayfly · Aquatic insect

Pond Olive

Cloeon dipterum

Size

6–9mm

Hook size

#16–14

Hatch window

Season June–OctoberPeak time 11:00–18:00

Water temperature

14° peak

8°20°

How fish feed on it

Here is the oddity worth knowing: the pond olive is viviparous. The female retains the eggs and releases live young after dark, which means the spent spinners are an early-MORNING item along the margins rather than the dusk fall everyone waits for. If you have been fishing spinner at last light and getting nowhere, that is why.

Flies that imitate this

Greenwell's Glory

CDC Olive Emerger

Ecology

Rivers & stillwaterTolerates poor water

Where you'll find this

British IslesPresent
IberiaPresent
The AlpsPresent
ScandinaviaPresent
Continental EuropePresent
Atlantic fringePresent

Present throughout

Identification

Cloeon dipterum is a species of mayfly with a Holarctic distribution. It is the most common mayfly in ponds in the British Isles and the only ovoviviparous mayfly in Europe. Males differ from females in having turbinate eyes.

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