When does the Slate Drake hatch?

May–October, typically Afternoon / evening. It starts from about 11°C, peaks around 16°C and tails off by 23°C.

What flies imitate the Slate Drake?

Mahogany Sparkle Dun, Adams Parachute, Isonychia, typically on a #14–12 hook.

How big is the Slate Drake?

Spinner stage: 11–14mm. That matches a #14–12 hook.

Mayfly · Aquatic insect

Slate Drake / Isonychia

Isonychia bicolor

Size

11–14mm

Hook size

#14–12

Hatch window

Season May–OctoberPeak time Afternoon / evening

Water temperature

16° peak

11°23°

How fish feed on it

The spinner fall is the better surface event for this species precisely because the emergence happens ashore. Evening, over riffles and the water below them.

Flies that imitate this

Mahogany Sparkle Dun

Adams Parachute

Isonychia

Ecology

Rivers onlySpate rivers

Where you'll find this

North America — EastPresent

Present throughout

Identification

Isonychia bicolor , the mahogany dun , is a species of brushlegged mayfly in the family Isonychiidae. It is found in southeastern Canada and the eastern United States.

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