When is the Brown Beetle most available to trout?

October–December, typically 19:00–23:00 (dusk into dark). It picks up from about 12°C, peaks around 17°C and tails off by 23°C.

What flies imitate the Brown Beetle?

Brown Beetle, Yellow Humpy, Foam Beetle, typically on a #10–8 hook.

How big is the Brown Beetle?

Adult stage: 12–16mm. That matches a #10–8 hook.

Terrestrial · Terrestrial

Brown Beetle

Costelytra giveni

Size

12–16mm

Hook size

#10–8

Hatch window

Season October–DecemberPeak time 19:00–23:00 (dusk into dark)

Water temperature

17° peak

12°23°

How fish feed on it

Nothing about a beetle or an ant belongs in the water, which is rather the point — once it's in, it isn't getting out, and a trout that's spent all summer learning this doesn't need convincing twice. The takes tend to be confident and unhurried, especially along undercut banks and under overhanging branches where windfall has been landing for as long as the tree's been there.

Flies that imitate this

Brown Beetle

Yellow Humpy

Foam Beetle

Ecology

Rivers & stillwaterLowland lochsPeaty loughs

Where you'll find this

New ZealandPresent

Present throughout

Identification

Costelytra giveni (mischaracterized as Costelytra zealandica prior to 2016), commonly known as New Zealand grass grub , is a scarab beetle that is endemic to New Zealand and is a prevalent pasture pest.