When does the NZ Green Stonefly hatch?

September–April, typically 11:00–16:00 (daytime). It starts from about 6°C, peaks around 11°C and tails off by 16°C.

What flies imitate the NZ Green Stonefly?

Green Beetle, typically on a #10–8 hook.

How big is the NZ Green Stonefly?

Adult stage: 15–20mm. That matches a #10–8 hook.

Stonefly · Aquatic insect

NZ Green Stonefly

Stenoperla prasina

Size

15–20mm

Hook size

#10–8

Hatch window

Season September–AprilPeak time 11:00–16:00 (daytime)

Water temperature

11° peak

6°16°

How fish feed on it

Adult insects on the water are inefficient — a caddis skittering to lay eggs, a stonefly blundering about after crawling out, neither built for elegance. Trout treat it as an easy meal and a bit of theatre at once, chasing a moving fly with more enthusiasm than they'd ever give a still one. Movement is the tell; a static adult imitation often just sits there unloved.

Flies that imitate this

Green Beetle

Ecology

Rivers & stillwaterAlpine riversSpate riversClean water only

Where you'll find this

New ZealandPresent

Present throughout

Identification

Stenoperla prasina ( Māori: ngarongaro wai ) is a species of stonefly belonging to the family Eustheniidae. This species is endemic to New Zealand and is classified as "Not Threatened" under the New Zealand Threat Classification System. It is found on the North, South and Stewart Island / Rakiura Islands as well as on Little Barrier Island. Although adults of this species are most often coloured bright green, this species can be coloured yellow. This species inhabits clean,...