When is the Heather Fly most available to trout?

August–September, typically 12:00–17:00. It picks up from about 6°C, peaks around 14°C and tails off by 22°C.

What flies imitate the Heather Fly?

Bibio, Black Gnat, typically on a #12–10 hook.

How big is the Heather Fly?

Adult stage: 9–13mm. That matches a #12–10 hook.

Terrestrial · Terrestrial

Heather Fly

Bibio pomonae

Size

9–13mm

Hook size

#12–10

Hatch window

Season August–SeptemberPeak time 12:00–17:00

Water temperature

14° peak

6°22°

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

Bibio

Black Gnat

Ecology

Rivers & stillwaterPeaty loughsSpate riversTolerates poor water

Where you'll find this

British IslesCommon
Atlantic fringeOccasional
ScandinaviaOccasional
Continental EuropeOccasional
The AlpsScarce

Common Occasional

Identification

Bibio pomonae , common name red-thighed St Mark's fly or heather fly , is a species of flies (Diptera) belonging to the family Bibionidae.