Here’s the latest advice from Robert Younghanz, Fly Talk’s resident “Bug Guy.”

Bundling up, grabbing your fly rod and trudging through drifts of snow in frigid temperatures may be considered nutty. But if you are fortunate enough to live in a state that allows fishing year round, with a bit of preparation and specialized knowledge the intrepid winter fly fisher will often be rewarded with solitude. The trick is trying to figure out what trout are eating when it’s 20 degrees on the river. It’s important to keep in mind that the very nature of fly fishing in the winter simplifies the bug selection process. The insect biomass is minimal.

I want to dispel the myth that the only insects that hatch in the winter months are midges. While Chrionomids can and do emerge year round, like all aquatic insects, in order to have a “successful” nuptial flight, ambient air temperatures need to be slightly over 40 degrees Fahrenheit. So on warmer days in the winter, it’s not at all uncommon to witness a variety of mayflies as well as midges hatching from the water. In tailwaters, I have witnessed insects attempting to emerge in temperatures far below 40 degrees, however their survival rate is negligible.

What very few people realize is that, even in the coldest of conditions, stoneflies have substantial winter fauna. The tiny winter black known to an aquatic entomologist as the Capniidae is a diminutive, flightless stonefly that crawls out of the water on to the snow and gets down to business even in sub zero temperatures. With close to 160 species of Capniids in North America, it’s common to see snow banks along virtually frozen rivers, riddled with these inconspicuous little insects. The nymph of this stone is slender, with a light brown elongated body and dark brown wing pads. A sparsely tied pheasant tail on a long dry fly hook in a #24-#26 is an excellent imitation of the nymphal stage to this winter river dweller.

The adults that make their way out of the river onto the bank and shed their exoskeleton are jet black. This occurs for one reason–to optimize heat absorption from the sun. Any small adult, black stonefly imitation in a size #20 should prove to be productive when the Tiny Winter Black is emerging. Having said this, it is doubtful that you will simply be able to walk into a fly shop and pick up a half a dozen size #20 black stonefly patterns, so you may be forced to tie up your own prototype. Fishing this pattern drowned can be especially effective.

So if you’re going to fish in winter, keep it simple. Don’t forget the small stoneflies! Choose small flies and light tippet. Dress warmly. Use hand warmers. Then take in all the peace and quiet that winter fly fishing has to offer.

Robert Younghanz is an aquatic entomologist, professional guide, and manager at the Angler’s Covey Fly Shop in Colorado Springs.