Photo by Jeff Tome

Capnia Overview

  • Family: Stonefly
  • Size: 6-8mm (Size 16-18)
  • Emergence: Late February through mid March
  • Emergence Time: Afternoons

Also known as the snow fly or little black stone, the first thing to say about Capnias is it’s rare to find fish taking them on the surface. The February water in Montana is often so cold the fish don’t move to take the relatively rapidly moving Capnia as they’re laying eggs.

Missoula guides carry a couple of Black Stimulators in a 16 or 18, but they’re not often utilized. It takes a truly early, warm spring to get the fish to the surface. It’s the nymph that’s important. We use a Black Perdigon in a size 16 or 18 to imitate this insect. As with all stoneflies, they emerge by crawling from the side of the river, so trout are found along the shallow shelves and drop-offs.

Capnias seem more prevalent on the Bitterroot River, but mostly because it’s our southern most river and is the first to start fishing. The snow fly is seen on Rock Creek, the Clark Fork River and the Blackfoot River. This is not an important hatch, but it is there from mid-February through early March. Sunny days with the temps above 40 will be the best time to see Capnia action, but again, it’s not a super important hatch.

Capnia Nymphs
Photo by Bob Henricks

Additional Capnia Resources