When does the Large Stonefly hatch?

March–May, typically 10:00–13:00. It starts from about 6°C, peaks around 9°C and tails off by 14°C.

What flies imitate the Large Stonefly?

Dark Needle, typically on a #6–4 hook.

How big is the Large Stonefly?

Adult stage: 20–28mm. That matches a #6–4 hook.

Stonefly · Aquatic insect

Large Stonefly

Dinocras cephalotes

Size

20–28mm

Hook size

#6–4

Hatch window

Season March–MayPeak time 10:00–13:00

Water temperature

9° peak

6°14°

How fish feed on it

The nymph crawls OUT of the river to emerge, up a rock or onto the bank, so there is no hatch on the water to fish — this is the thing to understand about every stonefly. What comes back is the egg-laying female, and she is the only surface event the species offers.

Flies that imitate this

Dark Needle

Ecology

Rivers & stillwaterAlpine riversSpate riversClean water only

Where you'll find this

British IslesPresent
IberiaPresent
The AlpsPresent
ScandinaviaPresent
Continental EuropePresent
Atlantic fringePresent

Present throughout